The need for sustainable fuels has resulted in the production of renewables from a wide range of sources, in particular organic fats and oils. The use of biofuel is becoming more widespread as a result of environmental and economic considerations. Several efforts have been made to substitute fossil fuels with green fuels. Ester molecules extracted from processed animal fats and organic plant materials are considered alternatives for the use in modern engine technologies. Two different methods have been adopted for converting esters in vegetable oils/animal fats into compounds consistent with petroleum products, namely the transesterification and the hydro-processing of ester bonds for the production of biodiesel. This review paper primarily focuses on conventional and renewable biodiesel feedstocks, the catalyst used and reaction kinetics of the production process.

An analysis approach considering gas-solids hydrodynamics, reaction kinetics and reacting species non-uniformity together in a dual-reactor system is presented for better understanding its mass and energy balance. It was achieved by a 3-dimensional comprehensive hydrodynamics and reaction model for the dual-reactor system, which was developed from the successfully verified 3-dimensional comprehensive combustion model for one circulating fluidized bed (CFB) system (Xu and Cheng, 2019). The developed model and analysis approach was successfully used on a 1?MW circulating fluidized bed – bubbling fluidized bed (CFB-BFB) dual-reactor system. Results showed the sensible and chemical energy between two reactors as well as the energy distributions in each reactor were balanced and they agreed well with the experimental measurements. The analysis approach indicated energy balance had a close relationship with the mass transfer in the CFB-BFB dual-reactor system. It may be applied in a design and operation optimization for a dual-reactor system.

In this research gasoil desalting was investigated from mass transfer point of view in an eductor liquid–liquid extraction column (eductor-LLE device). Mass transfer characteristics of the eductor-LLE device were evaluated and an empirical correlation was obtained by dimensional analysis of the dispersed phase Sherwood number. The Results showed that the overall mass transfer coefficient of the dispersed phase and extraction efficiency have been increased by increasing Sauter mean diameter (SMD) and decreasing the nozzle diameter from 2 to 1 mm, respectively. The effects of Reynolds number (Re), projection ratio (ratio of the distance between venturi throat and nozzle tip to venturi throat diameter, R_pr), venturi throat area to nozzle area ratio (R_th-n) and two phases flow rates ratio (R_Q) on the mass transfer coefficient (K) were determined. According to the results, K increase with increasing Re and R_Q and also with decreasing R_pr and R_th-n. Semi-empirical models of drop formation, rising and coalescence were compared with our proposed empirical model. It was revealed that the present model provided a relatively good fitting for the mass transfer model of drop coalescence. Moreover, experimental data were in better agreement with calculated data with AARE value of 0.085.

In this article, the thermal–hydraulic efficacy of a boehmite nanofluid with various particle shapes is evaluated inside a microchannel heat sink. The study is done for particle shapes of platelet, cylinder, blade, brick, and oblate spheroid at Reynolds numbers (Re) of 300, 800, 1300, and 1800. The particle volume fraction is assumed invariant for all of the nanoparticle shapes. The heat transfer coefficient (h), flow irregularities, pressure loss, and pumping power heighten by the elevation of the Re for all of the nanoparticle shapes. Also, the nanofluid having the platelet-shaped nanoparticles leads to the greatest h, and the nanofluid having the oblate spheroid particles has the lowest h and smallest pressure loss. In contrast, the nanofluid having the platelet-shaped nanoparticles leads to the highest pressure loss. The mean temperature of the bottom surface, thermal resistance, and temperature distribution uniformity decrease by the rise in the Reynolds number for all of the particle shapes. Also, the best distribution of the temperature and the lowest thermal resistance are observed for the suspension containing the platelet particles. Thereby, the thermal resistance of the nanofluid with the platelet particles shows a 9.5% decrement compared to that with the oblate spheroid particles at Re = 300. For all the nanoparticle shapes, the figure of merit (FoM) uplifts by elevating the Re, while the nanofluids containing the brick- and oblate spheroid-shaped nanoparticles demonstrate the highest FoM values.

It is known that the performances of multi-phase reactors depend on the operating parameters (the temperature and the pressure of the system), the phase properties, and the design parameters (the aspect ratio (AR), the bubble column diameter, and the gas sparger design). Hence, the precise design and the correct operation of multi-phase reactors depends on the understanding and prediction of the fluid dynamics parameters. This paper contributes to the existing discussion on the effect of operating and design parameter on multi-phase reactors and, in particular, it considers an industrial process (e.g., the LOPROX (low pressure oxidation) case study, which is typical example of two-phase bubble columns). Based on a previously-validated set of correlations, the influence of operating and design parameter on system performances is studied and critically analyzed. First, we studied the effects of the design parameter on the liquid–gas interfacial area, by keeping constant the fluid physical–chemical properties as well as the operating conditions; subsequently, we discussed for a fixed system design, the influence of the liquid phase properties and the operating pressure. In conclusion, this paper is intended to provide guidelines for the design and scale-up of multi-phase reactors.

Increasing importance of heat transfer in chemical engineering science causes that investigation in the field of enhancement techniques is always one of the up-to-date topics for study. In the current comparative analysis, the thermal enhancement and friction penalty are explored numerically for curved tubes via twisted configuration. To accomplish this, three common geometries namely helical, serpentine, and Archimedes spiral, are considered at different coil-pitches and twist-pitches as well as five Reynolds numbers in the laminar flow regime. The results exhibit noticeable enhancements (up to 60%) in the thermal performance of the twisted cases as compared to the smooth cases. The highest increases are recorded for the serpentine case, followed by the helical and spiral cases. It is found that these enhancements vary via coil-pitch and twist-pitch. Increasing coil-pitch and twist-pitch augments both heat transfer coefficient and pressure drop in all curved-twisted tubes, however, the effects of twist-pitch are more pronounced. To predict Nusselt number and friction factor, new correlations are also proposed. The maximum deviations of the predicted results compared to the simulated data are within ±5%.

To investigate the morphological evolution of the whole growth and aggregation processes of hydrate crystals near the gas–liquid interface, we used a high-pressure visual reactor with high-speed camera to capture the micromorphology of hydrate particles in a natural gas + pure water system with pressure from 2.6 to 3.6 MPa and sub-cooling from 4.7 to 6.23 ℃. The results showed that under low sub-cooling conditions, the amount and size of particles increased first and then decreased in the range of 0–330 μm, and the small particles always dominated. These particles can be roughly classified into two categories: planar flake particles and polyhedral solid particles. Then, the concept of maximum growth dominant particle size was proposed to distinguish the morphological boundary of growth and aggregation. In addition, the micro model was established to better reflect the effects of particle formation process and evolution mechanism near the gas–liquid interface under stirring condition. The results of this study can provide a guidance for flow assurance in multiphase pipeline.

Deterioration and loss of quality of vegetable oil is a big challenge in the food industry. This study investigated the synthesis of nickel ferrite (NiFe₂O₄) via co-precipitation method and its use for the removal of free fatty acids (FFAs) in deteriorated vegetable oil. NiFe₂O₄ was characterized using Fourier transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric (TG) analysis, Brunauer–Emmett–Teller (BET) surface area, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Synthesis of NiFe₂O₄ was confirmed by characterization, which revealed a BET surface area of 16.30 m²·g^-1 and crystallite size of 29 nm. NiFe₂O₄ exhibited an adsorption capacity of 145.20 L·kg^-1 towards FFAs with an 80.69% removal in a process, which obeys Langmuir isotherm and can be described by the pseudo-second-order kinetic model. The process has enthalpy (ΔH) of 11.251 kJ·mol^-1 and entropy (ΔS) of 0.038 kJ·mol^-1·K^-1 with negative free energy change (ΔG), which suggests the process to be spontaneous and endothermic. The quantum chemical computation analysis via density functional theory further revealed the sorption mechanism of FFAs by NiFe₂O₄ occurred via donor–acceptor interaction, which may be described by the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO). The study showed NiFe₂O₄ to be a potential means that can remove FFAs from deteriorated vegetable oil.

In the present study, the effects of relative humidity on filtrating coal-fired fly ash with hydrophobic poly tetra fluoroethylene (PTFE) membranes were investigated. The intergranular force of particulate matter at different RH conditions was measured by analyzing the critical angle between particles. Effects of humidity (from 30% to 70%) on filtration pressure drop and membrane fouling conditions were characterized. It was found the membrane showed optimal filtration resistance of 530 Pa at RH of 60% and the gas permeance can be maintained at 1440 m³·m^-2·h^-1·kPa^-1. Moreover, to optimize the operation parameters for this filtration system, effects of fly ash concentration, diameter, membrane pore size, and gas velocities were systematically investigated.

Cyclohexanol is a commonly used organic compound. Currently, the most promising industrial process for synthesizing cyclohexanol, by cyclohexene hydration, suffers from a low conversion rate and difficult separation. In this paper, a three-column process for catalytic distillation applicable in the hydration of cyclohexene to cyclohexanol was established to solve these. Simulation with Aspen Plus shows that the process has good advantages, the conversion of cyclohexene reached 99.3%, and the product purity was ≥99.2%. The stable operation of the distillation system requires a good control scheme. The design of the control scheme is very important. However, at present, the reactive distillation process for cyclohexene hydration is under investigation experimentally and by steady-state simulation. Therefore, three different plant-wide control schemes were established (CS1, CS2, CS3) and the position of temperature sensitive stage was selected by using sensitivity analysis method and singular value decomposition method. The Tyreus-Luyben empirical tuning method was used to tune the controller parameters. Finally, Aspen Dynamics simulation software was used to evaluate the performance of the three control schemes. By introducing ΔF ±20% and x_ENE ±5%, comparison the changes in product purity and yield of the three different control schemes. By comparison, we can see that the control scheme CS3 has the best performance.

A fundamental understanding of the effects of catalyst pellet structures and operation conditions on catalytic performance is crucial for the reactions limited by diffusion mass transfer. In this work, a numerical investigation has been carried out to understand the effect of catalyst pellet shapes (sphere, cylinder, trilobe and tetralobe) on the reaction-diffusion behaviors of CO methanation. The results reveal that the poly-lobe pellets with larger external specific surface area have shorter diffusion path, and thus result in higher effectiveness factors and CO conversion rates in comparison with the spherical and cylindrical pellets. The effects of operating conditions and pore structures on the trilobular catalyst pellet with high performance are further probed. Though lower temperature can contribute to larger effectiveness factors of pellets, it also brings about lower reaction rates, and pressure has little impact on the effectiveness factors of the pellets. The increase in porosity can reduce the pellet internal diffusion limitations effectively and there exists an optimal porosity for the methanation reaction. Finally, the height of the trilobular pellet is optimized under the given geometric volume, and the results demonstrate that the higher the trilobular catalyst, the better the reaction performance within the allowable mechanical strength range.

Designing an effective and stable composite photocatalyst is of significance for the further realization of practical applications. In this study, a series of CoP/CoO composites are successfully prepared by a straight one-step phosphating method. The reasonable design and controllable preparation of CoP/CoO composite make it exhibit improved photocatalytic performance for overall water splitting and excellent stability under visible light irradiation in comparison with pure CoO, which is derived from the CoP nanoparticles well dispersed on the (111) facets of CoO octahedrons, intimate interface between them and efficiently accelerated of photo-induced electrons from CoO to CoP. This study presents a simple method to design highly-effective composite photocatalysts for overall water splitting to meet the energy demand.

The engineering of highly efficient and stable heterogeneous catalysts for catalytic conversion of CO₂ to high value-added products is highly desirable but presents a great challenge. Herein, we reported the synthesis of a series of multifunctional IL@H-Zn/Co-ZIF composite catalysts with a unique porous hollow capsule structure and encapsulated amino-functionalized ionic liquids (ILs). The unique hollow capsule structure of IL@H-Zn/Co-ZIF provides sufficient space for loading active ILs ([C₂NH₂Mim⁺][Br^-]) and fast mass transfer of substrate molecules during catalysis. Furthermore, the microporous Zn-ZIF shell can effectively avoid the leaching of active ILs. Benefiting from the unique hollow structure, the resultant IL@H-Zn/Co-ZIF demonstrated excellent catalytic performance (>95% yield), and good recyclability (still remained about 90% activities after 5 cycles) when applied in the CO₂ cycloaddition reaction under solvent and co-catalyst free conditions.

Combined effects of obstacles and fine water mist on a methane-air explosion of a semi-closed pipe were investigated experimentally. In this study, the diameter of the water mist, the location, and the number of obstacles was considered. The results demonstrated that 5 μm water mist present a significant suppression affected while 45 μm shows a slight promotion effected on a gas explosion of the condition without obstacles. In the presence of an obstacle, however, the inhibitory effect of 5 μm water veils of mist dropped significantly during flame propagation, and the effect of 45 μm water veils of mist changed from the enhancement of inhibition, and its inhibitory effect was significant. The inhibitory effect of 45 μm water veils of mist on gas explosion weakened firstly and then enhanced with the increasing distance between obstacle location from the ignition location as well as in several obstacles.

In refineries, some hydrogen-rich streams contain considerable light hydrocarbons that are important raw materials for the chemical industry. Integrating hydrogen networks with light hydrocarbon recovery can enhance the reuse of both hydrogen and light hydrocarbons. This work proposes an automated method for targeting hydrogen networks with light hydrocarbon recovery. A pinch-based algebraic method is improved to determine the minimum fresh hydrogen consumption and hydrogen sources fed into the light hydrocarbon recovery unit automatically. Rigorous process simulation is conducted to determine the mass and energy balances of the light hydrocarbon recovery process. The targeting procedures are developed through combination of the improved pinch method and rigorous process simulation. This hybrid method is realized by coupling the Matlab and Aspen HYSYS platforms. A refinery hydrogen network is analyzed to illustrate application of the proposed method. The integration of hydrogen network with light hydrocarbon recovery further reduces fresh hydrogen requirement by 463.0 m³·h^-1 and recovers liquefied petroleum gas and gasoline of 1711.5 kg·h^-1 and 643 kg·h^-1, respectively. A payback period of 9.2 months indicates that investment in light hydrocarbon recovery is economically attractive.

This work presents the implementation of fuzzy logic control (FLC) on a microbial electrolysis cell (MEC). Hydrogen has been touted as a potential alternative source of energy to the depleting fossil fuels. MEC is one of the most extensively studied method of hydrogen production. The utilization of biowaste as its substrate by MEC promotes the waste to energy initiative. The hydrogen production within the MEC system, which involves microbial interaction contributes to the system’s nonlinearity. Taking into account of the high complexity of MEC system, a precise process control system is required to ensure a well-controlled biohydrogen production flow rate and storage application inside a tank. Proportional-derivative-integral (PID) controller has been one of the pioneer control loop mechanism. However, it lacks the capability to adapt properly in the presence of disturbance. An advanced process control mechanism such as the FLC has proven to be a better solution to be implemented on a nonlinear system due to its similarity in human-natured thinking. The performance of the FLC has been evaluated based on its implementation on the MEC system through various control schemes progressively. Similar evaluations include the performance of Proportional-Integral (PI) and PID controller for comparison purposes. The tracking capability of FLC is also accessed against another advanced controller that is the model predictive controller (MPC). One of the key findings in this work is that the FLC resulted in a desirable hydrogen output via MEC over the PI and PID controller in terms of shorter settling time and lesser overshoot.

Sulfate mass transfer coefficient (MTC) is a sensitive parameter to evaluate the kinetic leakage of anion exchange resin used in condensate polishing system of thermal and nuclear power plant. However, a sufficiently precise determination method has not been well established. In this paper, the final expression of sulfate MTC derived based on plug flow reactor model is the same as Harries’ model, which is widely acknowledged in this field. In the determining system we constructed, in-situ calibration of the concentration of sulfate and its cation conductivity was conducted and sulfate MTCs of four typical strongly basic anion exchange resin samples were determined. The systematic error is 8.26% and the calibrated curve used for quantifying sulfate is obtained. The repeatability and reproducibility standard deviation are 0.05×10^-4 m·s^-1 and 0.07×10^-4 m·s^-1 respectively, which are lower than previous works. By controlling test condition accurately, this study has developed a more precise sulfate MTC determining method. This method provides a basis for further research.

Recent research on deterministic methods for circulating cooling water systems optimization has been well developed. However, the actual operating conditions of the system are mostly variable, so the system obtained under deterministic conditions may not be stable and economical. This paper studies the optimization of circulating cooling water systems under uncertain circumstance. To improve the reliability of the system and reduce the water and energy consumption, the influence of different uncertain parameters is taken into consideration. The chance constrained programming method is used to build a model under uncertain conditions, where the confidence level indicates the degree of constraint violation. Probability distribution functions are used to describe the form of uncertain parameters. The objective is to minimize the total cost and obtain the optimal cooling network configuration simultaneously. An algorithm based on Monte Carlo method is proposed, and GAMS software is used to solve the mixed integer nonlinear programming model. A case is optimized to verify the validity of the model. Compared with the deterministic optimization method, the results show that when considering the different types of uncertain parameters, a system with better economy and reliability can be obtained (total cost can be reduced at least 2%).

The operation of dehydration is very important in the process of gas transportation. This study aims to evaluate the application feasibility of CO₂ dehydration using triethylene glycol, which is also called TEG for short. Aspen Plus software was used to simulate the dehydration process system of CO₂ gas transportation using TEG dehydration. Parameter analysis and process improvement were carried out for the simulation of dehydration process. At first, a sensitivity analysis was conducted to analyze and optimize operating conditions of conventional CO₂-TEG dehydration process system. Subsequently, a recycle unit was introduced into the conventional CO₂-TEG dehydration process system, it can be found that the improved process system with the recycle unit has a higher CO₂ recovery rate which was about 9.8% than the conventional one. Moreover, the improved process system showed excellent operation stability through the comparison of simulation results of several processes with various water contents in their feed gases. Although the energy consumption is increased by about 2%, the improved process was economically and technically feasible for the long-term availability of CO₂ pipeline transportation. The simulated results showed that the improved CO₂-TEG process system has promising application prospects in CO₂ dehydration of CO₂ gas transportation with high stability.

A hydrogen liquefaction concept with an innovative configuration and a capacity of 4 kg·s^-1 (345.6 t·d^-1) is developed. The concept involves an ammonia absorption refrigeration system for the pre-cooling of hydrogen and MR streams from 25 ℃ to -30 ℃. The ammonia absorption refrigeration system is fed by exhaust gases of the Parand gas power plant that are normally dissipated to the environment with a temperature of 546 ℃. The simulation is performed by Aspen HYSYS V9.0, using two separate equations of state for simulating hydrogen and MR streams to gain more accurate results especially for ortho-para conversion. Results show that conversion enthalpy estimated by Aspen HYSYS, fits very well to the experimental data. Determining the important independent variables and composition of MRs are done using trial and error procedure, a functional and straightforward method for complicated systems. The minimum temperature limit in the cooling section is lowered, and an ortho-para converter is implemented in this section. The proposed concept performs well from energy aspects and leads to COP and SEC equal to 0.271 and 4.54 kW·h·kg^-1, respectively. The main advantage of this study is in the low SEC, eliminating the losses of the distribution network, and improving the ability of the hydrogen liquefaction for energy storage in off-peak times.

This study describes the adsorption behavior of three arylthiophene derivatives namely: 2-(4-amidino-3-fluorophenyl)-5-[4-methoxy phenyl] thiophene dihydrochloride salt (MA-1217), 2-(4-amidinophenyl)-5-[4-chlorophenyl] thiophene dihydrochloride salt (MA-1316) and 2-(4-amidino-3-fluorophenyl)-5-[4-chlorophenyl]thiophene dihydrochloride salt (MA-1312) at C-steel in 1.0 mol·L^-1 HCl interface using experimental and theoretical studies. Electrochemical and mass loss measurements showed that the inhibition efficiency (IE) of the arylthiophene derivatives increases with increasing concentrations and exhibited maximum efficiency 89% at 21×10^-6 mol·L^-1 (MA-1217) by mass loss method. The investigated arylthiophene derivatives obey the Langmuir adsorption isotherm. From polarization studies the arylthiophene derivatives act as mixed-type inhibitors. Surface analysis were carried out and discussed. The mode of orientation and adsorption of inhibitor molecules on C-steel surface was studied using molecular dynamics (MD) simulations. Quantum chemical parameters as well as the radial distribution function indices and binding energies confirm the experimental results.

Over exploitation of non-renewable energy reserves will lead to increase in price of petroleum fuels. Therefore there is a need for suitable and sustainable substitutes (renewable resource) for conventional fuels. In this study, an efficient and environmental friendly method for production of bio-diesel from Pongamia (Karanja) oil has been developed using a solar reactor. During the experimental study, the maximum temperature attained by the pongamia oil during the transesterification process was 64.1 ℃. The transesterification reaction was studied by varying different parameters such as reactant flow rate (5–20 L·h^-1), stirring speed (150–450 r·min^-1), catalyst mass loading (0.5%–2%) and methanol to oil ratio (3:1 to 15:1). The maximum biodiesel yield was 83.11% at a flow rate of 5 L·h^-1, stirring speed of 350 r·min^-1, a methanol to oil ratio of 15:1, catalyst mass loading of 1% and reaction time of 270 min. The physical and chemical properties of biodiesel was analyzed as per American Society for Testing Materials (ASTM) standards and it had density of 938 kg·m^-3, viscosity (28.7×10^-6 m²·s^-1), acid value (9.45 mg KOH·(g oil)^-1) and flash point (215 ℃). The energy efficiency of solar heating process was determined by comparing the net energy ratio of direct heating process and solar heating process. For solar heating the net energy ratio (NER) was found to be 31.85 against 5.73 for direct heating. Similarly, net energy efficiency index was calculated for 10 kg production scale and was found to be increasing when scaled up which means that the solar heating process is more effective even in scaled up production.

To preserve the environment for civilization, we should remove the pollutants like toxic dyes by friendly and cost efficacious method. In this study, the effect of surfactants or mixed surfactants on physicochemical, optical and adsorption properties of ternary mixed oxide CeO₂-ZrO₂-Al₂O₃ (CZA) are investigated. The ternary mixed oxide CZA was prepared by surfactants or mixed surfactants assisted ultrasonic co-precipitation method. The physicochemical and optical properties are estimated by different techniques like XRD, TEM, EDX, FTIR, S_BET and UV–Vis/DR. The CZA_T and CZA_C have hybrid shapes and high surface area. The adsorption properties of ternary mixed oxides adsorbents were characterized by sono-removing anionic dyes such as Congo red (CR) and Remazol red RB-133 (RR). The different factors like contact time, different dye concentrations and temperatures also studied. The kinetics and isotherms applications showed that, the adsorption process was followed pseudo second order kinetics and the Freundlich isotherm model. Also, the adsorption is spontaneous and endothermic process through the thermodynamic study. Finally, the results showed that the ternary mixed oxide nano-adsorbent (CeO₂-ZrO₂-Al₂O₃₎ is promising and functional materials for anionic dye sweep from wastewater.

Natural gas hydrate inhibitor has been serving the oil and gas industry for many years. The development and search for new inhibitors remain the focus of research. In this study, the solution polymerization method was employed to prepare poly(N-vinyl caprolactam-co-butyl methacrylate) (P(VCap-BMA)), as a new kinetic hydrate inhibitor (KHI). The inhibition properties of P(VCap-BMA) were investigated by tetrahydrofuran (THF) hydrate testing and natural gas hydrate forming and compared with the commercial KHIs. The experiment showed that PVCap performed better than copolymer P(VCap-BMA). However, low doses of methanol or ethylene glycol are compounded with KHIs. The compounding inhibitors show a synergistic inhibitory effect. More interesting is the P(VCap-BMA)-methanol system has a better inhibitory effect than the PVCap-methanol system. 1% P(VCap-BMA) + 5% methanol presented the best inhibiting performance at subcooling 10.3 ℃, the induction time of natural gas hydrate was 445 min. Finally, the interaction between water and several dimeric inhibitors compared by natural bond orbital (NBO) analyses and density functional theory (DFT) indicated that inhibitor molecules were able to form the hydrogen bond with the water molecules, which result in gas hydrate inhibition. These exciting properties make the P(VCap-BMA) compound hydrate inhibitor promising candidates for numerous applications in the petrochemical industry.

Cadmium (Cd), lead (Pb), and hexavalent chromium (Cr(VI)) are often found in soils and water affected by metal smelting, chemical manufacturing, and electroplating. In this study, synthetic iron sulfide nanoparticles (FeS NPs) were stabilized with carboxymethyl cellulose (CMC) and utilized to remove Cr(VI), Cd, and Pb from an aqueous solution. Batch experiments, a Visual MINTEQ model, scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectrometer (XPS) analysis were used to determine the removal efficiencies, influencing factors, and mechanisms. The FeS NP suspension simultaneously removed Cr(VI), Cd, and Pb from an aqueous solution. The concentrations of Cr(VI), Cd, and Pb decreased from 50, 10, and 50 mg·L^-1 to 2.5, 0.1, and 0.1 mg·L^-1, respectively. The removal capacities were up to 418, 96, and 585 mg per gram of stabilized FeS NPs, respectively. The acidic conditions significantly favored the removal of aqueous Cr(VI) while the alkaline conditions favored the removal of Cd and Pb. Oxygen slightly inhibited the removal of Cr(VI), but it had no significant influence on the removal of Cd and Pb. A potential mechanism was proposed for the simultaneous removal of Cr(VI), Cd, and Pb using FeS NPs. The interactions of the three heavy metals involved a cationic bridging effect on Cr(VI) by Cd, an enhanced adsorption effect on Cd by [Cr,Fe](OH)₃, precipitation of PbCrO₄, and transformation of PbCrO₄ to PbS. Therefore, FeS NPs have a high potential for use in the simultaneous removal of Cr(VI), Cd, and Pb from contaminated aqueous solutions.

Bacterial cellulose doped with P and Cu was used as a catalyst for a microbial fuel cell (MFC) cathode, which was then used to treat ethanol fermentation stillage from food waste. Corresponding output power, coulombic efficiency (CE), and biological toxicity were detected. Through a series of characterization experiments, the addition of the cathode catalyst was found to improve catalytic activity and accelerate the consumption of the substrate. The resulting maximum output power was 572.16 mW·m^-2. CE and the removal rate of chemical oxygen demand (COD) in the fermentation stillage by P-Cu-BC reached 26% and 64.5%, respectively. The rate of biotoxicity removal by MFC treatment reached 84.7%. The aim of this study was apply a novel catalyst for MFC and optimize the treatment efficiency of fermentation stillage.

The recycling of waste printed circuit board (WPCBs) is of great significance for saving resources and protecting the environment. In this study, the WPCBs were pyrolyzed by microwave and the contained valuable metals Cu, Sn and Pb were recovered from the pyrolyzed WPCBs. The effect of pyrolysis temperature and time on the recovery efficiency of valuable metals was investigated. Additionally, the characterization for morphology and surface elemental distribution of pyrolysis residues was carried out to investigate the pyrolysis mechanism. The plastic fiber boards turned into black carbides, and they can be easily separated from the metals by manual. The results indicate that 91.2%, 96.1% and 94.4% of Cu, Sn and Pb can be recovered after microwave pyrolysis at 700 ℃ for 60 minutes. After pyrolysis, about 79.8% (mass) solid products, 11.9% (mass) oil and 8.3% (mass) gas were produced. These gas and oil can be used as fuel and raw materials of organic chemicals, respectively. This process provides an efficient and energy-saving technology for recovering valuable metals from WPCBs.

Metal-based perovskite oxides have contributed significantly to the advanced oxidation processes (AOPs) due to their diverse active sites and excellent compositional/structural flexibility. In this study, we specially designed a perovskite oxide with abundant oxygen vacancies, SrCo_0.8Fe_0.2O₃ (SCF), and firstly applied it as a catalyst in peroxymonosulfate (PMS) activation towards organic pollutants degradation. The result revealed that the prepared SCF catalyst exhibited excellent performance on organic compounds degradation. Besides, SCF showed much better activity than La_0.5Sr_0.5Co_0.8Fe_0.2O₃ (LSCF) in terms of reaction rate and stability for the degradation of the organic compounds. Based on the analysis of scanning electron microscope, transmission electron microscope, X-ray diffraction, N₂ adsorption–desorption, X-ray photoelectron spectroscopy and electron paramagnetic resonance, it was confirmed that the perovskite catalysts with high content of Sr doping at A-site could effectively create a defect-rich surface and optimize its physicochemical properties, which was responsible for the excellent heterogeneous catalytic activity of SCF. SCF can generate three highly active species: ¹O₂, SO^-₄· and ·OH in PMS activation, revealing the degradation process of organic compounds was a coupled multiple active species in both radical and nonradical pathway. Moreover, it was mainly in a radical pathway in the degradation through PMS activation on SCF and SO^-₄· radicals produced were the dominant species in SCF/PMS system. This study demonstrated that perovskite-type catalysts could enrich OVs efficiently by doping strategy and regulate the PMS activation towards sulfate radical-based AOPs.

At present, metal ions from spent lithium-ion batteries are mostly recovered by the acid leaching procedure, which unavoidably introduces potential pollutants to the environment. Therefore, it is necessary to develop more direct and effective green recycling methods. In this research, a method for the direct regeneration of anode materials is reported, which includes the particles size reduction of recovered raw materials by jet milling and ball milling, followed by calcination at high temperature after lithium supplementation. The regenerated LiNi_0.5Co_0.2Mn_0.3O₂ single-crystal cathode material possessed a relatively ideal layered structure and a complete surface morphology when the lithium content was n(Ni + Co + Mn):n(Li) = 1:1.10 at a sintering temperature of 920 ℃, and a sintering time of 12 h. The first discharge specific capacity was 154.87 mA·h·g^-1 between 2.75 V and 4.2 V, with a capacity retention rate of 90% after 100 cycles.

Olive mills wastewater (OMW) exhibit substantial contaminated properties due to their content of phenolic constituents and organic substances. The purpose of this work was the investigation of the efficiency of clay materials for the adsorption of phenolic compounds, which are contained in OMW. Furthermore, thermal activation of the clay took place in order to improve phenolic compounds uptake and afterwards, desorption process was studied. The adsorbent was characterized using XRD, XRF and BET surface area analyses. The adsorption efficiency of phenolic compounds by raw and calcined clay at 600 ℃ was 77.61% and 84.21%, respectively at acidic pH. The values of Gibbs free energy indicated that adsorption process is spontaneous and beneficial at higher temperatures. Alkaline medium was propitious for phenolic compounds desorption. The obtained results showed that natural clay could be used as a low-cost adsorbent for OMW treatment.

In this work, modified g-C₃N₄ was fabricated successfully by calcination of ionic liquid (IL) and urea. The addition of IL changed the polymerization mode of urea, induced the self-assembly of urea molecules, modified the morphological structure of the tightly packed g-C₃N₄, and extended the electron conjugation system. When using 1-butyl-3-methylimidazolium chloride ([Bmim]Cl) as a modifier, the heteroatom Cl could be inserted into the g-C₃N₄ to optimize the electronic structure. The results of characterizations indicate that the unique structure of modified g-C₃N₄ has an expanded electron delocalization range, introduces an interlayer charge transmission channel, promotes the charge transmission, reduces the band gap, enhances the absorption of visible light, and inhibits electron-hole recombination. Modified g-C₃N₄ showed excellent photocatalytic performance for the degradation of rhodamine B and tetracycline. Furthermore, the effect of different anions in 1-butyl-3-methylimidazolium salts ([Bmim]Cl, [Bmim]Br, [Bmim][BF₄], and [Bmim][PF₆]) on the structure and function of g-C₃N₄ are discussed.

Supercapacitor is a new type of energy storage device, which has the advantages of high-power property and long cycle life. In this study, three-dimensional graphene (3D-GN) with oxygen doping and porous structure was prepared from graphene oxide (GO) by an inexpensive sodium chloride (NaCl) template, as a promising electrode material for the supercapacitor. The structure, morphology, specific surface area, pore size, of the sample were characterized by XRD, SEM, TEM and BET techniques. The electrochemical performances of the sample were tested by CV and CDC techniques. The 3D-GE product is a three-dimensional nano material with hierarchical porous structures, its specific surface area is much larger than that of routine stacked graphene (GN), and it contains a large number of mesoporous and macropores, a small amount of micropores. The capacitance characteristics of the 3D-GN electrode material are excellent, showing high specific capacitance (173.5 F·g^-1 at 1 A·g^-1), good rate performance (109.2 F·g^-1 at 8 A·g^-1) and long cycle life (88% capacitance retention after 10,000 cycles at 8 A·g^-1)

The thermodynamic properties of MgCaSi and its mother phase Ca₂Si are comparatively investigated from ab initio calculations and quasi-harmonic Debye-Grüneisen model. At 0 K, MgCaSi is more thermodynamically stable. Under high temperature, the advantage of higher thermodynamically stability of MgCaSi is reduced, originating from the less negative entropy contribution because the thermodynamic entropy of MgCaSi increases more slowly with temperature and the entropy values are slightly smaller. With increasing temperature, the anti-softening ability for MgCaSi is slightly smaller due to the slightly faster decrease trend of bulk modulus than that of Ca₂Si, although the bulk modulus of MgCaSi is higher in the whole temperature range considered. The thermal expansion behaviors of both MgCaSi and Ca₂Si exhibit similar increase trend, although thermal expansion coefficient of MgCaSi is slightly lower and the increases is slightly slower at lower temperature. The isochoric heat capacity and isobaric heat capacity of MgCaSi and Ca₂Si rise nonlinearly with temperature, and both are close to the Dulong–Petit limit at high temperature due to the negligibly small electronic contribution. The Debye temperature of both phases decrease with increasing temperature, and the downtrend for MgCaSi is slightly faster. However, MgCaSi possess slightly higher Debye temperature, implying the stronger chemical bonds and higher thermal conductivity than the mother phase Ca₂Si. The Grüneisen parameter of MgCaSi and Ca₂Si increase slightly with temperature, the values of MgCaSi are slightly larger. The investigation of electronic structures shows that with substitution of partial Ca by Mg in Ca₂Si, the stronger MgSi, MgCa and SiSi covalent bonds are formed, and plays a very significant role for the structural stability and mechanical properties.

Today, a variety of pesticides are used to fight plant pests in the world. The entry of these resistant pollutants into water resources can have devastating effects on human health and the environment, hence their removal from the environment is a vital task. In the present work, the magnetic iron-based metal–organic framework (Fe₃O₄/MIL-101 (Fe)) was synthesized by a simple and feasible method and characterized by FT-IR, XRD, BET, FESEM, TEM, TGA, and VSM techniques. The synthesized nanocomposite was successfully applied for the removal of fenitrothion (FEN) pesticide from the aqueous solutions. The isothermal and kinetic models were also investigated. The Langmuir isotherm model (type I) and pseudo-second-order kinetic model were more consistent in the adsorption process. The thermodynamic parameters of fenitrothion sorption were also calculated. The results revealed that the adsorption of fenitrothion onto Fe₃O₄/MIL-101 (Fe) was spontaneous and endothermic under optimized conditions. Moreover, the removal efficiency of FEN was predicted using the developed fuzzy logic model. Four input variables including the initial concentration of FEN (mg·L^-1), pH of the solution, adsorbent dosage (mg), and contact time (min) versus removal efficiency as output were fuzzified by the usage of an artificial intelligence-based method. The fuzzy subsets consisted of Triangular and Trapezoidal membership functions (MFs) with six levels and a total of 23 rules in IF-THEN format which was applied on a Mamdani inference system. The obtained coefficient of determination value (=0.98205) proved the excellent accuracy of the fuzzy logic model as a powerful tool for the prediction of FEN removal efficiency.