Sips Isotherm Research Articles

Response surface methodology optimization of sodium diclofenac adsorption using activated carbon derived from falcata tree sawdust

The presence of sodium diclofenac in water is a significant problem due to its adverse effects on terrestrial and aquatic organisms. Thus, this study investigated the Falcata tree sawdust as the precursor of activated carbon for the adsorption of diclofenac in an aqueous solution. The characterization of falcata tree sawdust-activated carbon (FTSAC) was evaluated by SEM and FTIR analysis. The activated falcata sawdust converted to activated carbon has a 30 % yield. The optimal values for the operating parameters, FTSAC dosage, initial sodium diclofenac concentration, reaction time and pH, were determined using the central composite design (CCD) of the response surface methodology (RSM). The optimal removal efficiency suggested by CCD is 93.98 % with the optimum conditions of parameters of 0.80 g FTSAC dosage, 200 ppm initial sodium diclofenac concentration, 20 min reaction time, and pH 4. These optimal values of parameters were validated by an actual experiment, and the result (average removal efficiency: 92.08 %) is within a 95 % confidence interval. On the other hand, the pseudo-second-order (R2 = 0.9991) kinetic model depicts the rate of absorption of FTSAC adsorbing SD. Moreover, the Langmuir-Freundlich isotherm or Sips isotherm model (R2 = 0.9904) is the best-fit model that describes the heterogeneous adsorption dynamics of FTSAC surfaces. This study indicates that falcata sawdust can serve as a promising and viable alternative raw material to produce activated carbon.

Enhancing kaolin's structure for efficient removal of lead ions from aqueous solutions

This research demonstrates a novel methodology for structurally modifying kaolin clay to efficiently remove toxic lead ions from water through adsorption. Kaolin was systematically treated with hydrochloric acid, cetylpyridinium chloride surfactant, and calcium chloride to enhance its physico-chemical properties. BET surface area analysis, transmission electron microscopy, scanning electron microscopy, and BJH pore size measurements confirmed successful intercalation of surfactants between kaolin sheets, increasing the surface area from 43.2 to 57.1 m2 g-1 and inducing larger mesopores. Operational factors such as pH, dosage of adsorbent, time spent in contact, starting lead concentration, and temperature were tuned using batch adsorption tests. Maximum lead uptake of 29.58 mg g-1 was attained at pH 5, 20 mg adsorbent dose, 30 mg L-1 initial lead concentration, 80 min contact time, and 30°C temperature. Pseudo-second order kinetics and Sips isotherm models aptly characterized the adsorption, indicating chemisorption on heterogeneous sites. Positive enthalpy and entropy changes signified an endothermic and irreversible process. Regeneration studies demonstrated stable performance over five adsorption-desorption cycles. This comprehensive methodology integrates acid, surfactant, and cationic treatments to synthesize an eco-friendly kaolin adsorbent with enhanced selectivity and adsorption capacity for removing toxic lead from water.

Chitosan/Poly(maleic acid-alt-vinyl acetate) Hydrogel Beads for the Removal of Cu2+ from Aqueous Solution.

Covalent cross-linked hydrogels based on chitosan and poly(maleic acid-alt-vinyl acetate) were prepared as spherical beads. The structural modifications of the beads during the preparation steps (dropping in liquid nitrogen and lyophilization, thermal treatment, washing with water, and treatment with NaOH) were monitored by FT-IR spectroscopy. The hydrogel beads have a porous inner structure, as shown by SEM microscopy; moreover, they are stable in acidic and basic pH due to the covalent crosslinking. The swelling degree is strongly influenced by the pH since the beads possess ionizable amine and carboxylic groups. The binding capacity for Cu2+ ions was examined in batch mode as a function of sorbent composition, pH, contact time, and the initial concentration of Cu2+. The kinetic data were well-fitted with the pseudo-second-order kinetic, while the sorption equilibrium data were better fitted with Langmuir and Sips isotherms. The maximum equilibrium sorption capacity was higher for the beads obtained with a 3:1 molar ratio between the maleic copolymer and chitosan (142.4 mg Cu2+ g-1), compared with the beads obtained using a 1:1 molar ratio (103.7 mg Cu2+ g-1). The beads show a high degree of reusability since no notable decrease in the sorption capacity was observed after five consecutive sorption/desorption cycles.

β-cyclodextrin-functionalized coffee husk biochar for surfactant adsorption

In this study, biochar was produced from coffee husks and further functionalized with β-cyclodextrin to remove sodium dodecylbenzenesulfonate (SDBS) and cetylpyridinium chloride (CPC) surfactants from aqueous solution. The effect of pre-pyrolysis treatment of the coffee husks with NaOH, as well as the type of crosslinking agent, on the functionalization was evaluated. The biochars were characterized by FTIR, Raman spectroscopy, TGA, SEM, EDS, and chemical analysis. Adsorption kinetics and equilibrium isotherms were investigated in aqueous solutions. SDBS adsorption was not favored under all the investigated materials and conditions. The functionalized biochars showed better CPC removal (57.5 mg g−1 for glutaraldehyde functionalized biochar, and 113.6 mg g−1 for epichlorohydrin functionalized biochar) compared with non-functionalized biochars (55.8 mg g−1 for non-treated biochar and 35.1 mg g−1 for NaOH pre-treated biochar). The functionalized materials showed better CPC adsorptive capacity than prior literature reports. The adsorption data of CPC fit best to the Elovich kinetic model and Sips isotherm. Thermodynamic studies revealed that CPC adsorption is an endothermic process. The results indicated that β-cyclodextrin functionalization increased CPC removal, but electrostatic interactions acted as important mechanism for the adsorption. This work extends the range of applications for β-cyclodextrin-functionalized biochars by offering new design strategies for developing biochar-based adsorbents aimed at surfactant wastewater removal.

Hydrothermal synthesis of pore-expanded hydroxyapatite for enhanced Cu2+ adsorption from aqueous solutions

This paper describes the hydrothermal synthesis of a pore-expanded hydroxyapatite (PE-HAp) from fine–grained calcareous sludge using a cetyltrimethylammonium bromide (CTAB) as a template and 1,3,5-trimethylbenzene (TMB) as a pore expander for the removal of Cu2+ ions from aqueous solutions. The PE-HAp was characterized using XRD, SEM, DTA/TGA and BET surface analysis. Adsorption behavior was assessed using Langmuir, Freundlich, Dubinin–Radushkevich, Temkin and Sips isotherms. In a solution with an initial Cu2+ concentration of 200 mg L-1 and a pH of 5.0, the highest Cu2+ removal efficiency was achieved using PE-HAp synthesized at a hydrothermal temperature of 180 °C at a concentration of 15 g/L over a period of 60 min. Using Langmuir isotherms, the highest single-layer adsorption capacity value was 9.90 mg g-1. Gibbs free energy (ΔG°), changes in enthalpy (ΔH°), and changes entropy change (ΔS°) revealed that the adsorption of Cu2+ on PE-HAp was spontaneous and exothermic. The PE-HAp synthesized in this study is a promising material for the removal of Cu2+ from aqueous solutions.

Investigation of hydrogen uptake capacity for FAU, MOR, MTW, MWW

In this study, the hydrogen storage properties of various synthetic zeolites, including Zeolite Y (FAU), Mordenite (MOR), ZSM-12 (MTW), and MCM-22 (MWW) are determined at 77 K and atmospheric pressure. The structures of the zeolites are characterized by XRD, ICP-OES, FE-SEM, TGA and N2 adsorption-desorption isotherms. The results show that H-MCM-22 zeolite has the highest hydrogen storage capacity at 1.0 bar with 1.19 wt%, followed by H-MOR zeolite with 1.05 wt%, H–Y zeolite with 0.75 wt% and H-ZSM-12 zeolite with 0.60 wt%. The hydrogen adsorption data on FAU, MOR, MTW, and MWW at 77 K obey the Sips isotherm model. The experimental data show that the ultra-micropore volume of the zeolite is effective in hydrogen adsorption at low-pressure ranges. In addition, increasing the aluminum content of the zeolite increases the hydrogen adsorption capacity of the zeolite at atmospheric pressure. Therefore, zeolites with channel sizes close to the kinetic diameter of a hydrogen molecule, large cage volumes, and high aluminum content are potential candidates for energy storage applications.

Study of the Adsorption of Anionic Surfactants on Carbonate Rocks: Characterizations, Experimental Design, and Parameter Implementation

Controlling or reducing the adsorption of surfactants on reservoir rock surfaces has been a challenging task in enhanced oil recovery (EOR) methods, as it directly affects the cost-effectiveness of the projects. The adsorption of surfactants on rock surfaces can modify their hydrophobicity, surface charge, and other important parameters that govern EOR processes, such as reducing the interfacial tension between water and oil and increasing permeability. Therefore, understanding the adsorption mechanism on rocks is essential for developing alternatives that improve the effectiveness of these processes. In this work, the adsorption of surfactants on carbonate materials was evaluated considering variations in temperature, contact time, and surfactant concentration. The surfactants used were derived from vegetable oils, aiming for a sustainable approach: saponified coconut oil (SCO), saponified babassu coconut oil (SBCO), and saponified castor oil (SMO). The finite bath method was used, resulting in adsorption efficiencies of 85.74%, 82.52%, and 45.30% for SCO, SBCO, and SMO, respectively. The Sips isotherm and the pseudo-second-order model were found to be suitable for characterizing these systems. The simulation of SCO adsorption isotherms on limestone by the Langmuir model was more accurate than that using the Freundlich model. The limestone showed a negative surface charge of approximately −35.0 mV at pH 6.5; this negative charge varied over a wide pH range. These zeta potential data for the samples confirmed that hydrophobic interactions played an important role in the adsorption of the surfactants. Thermodynamic evaluation indicated spontaneous and endothermic adsorption of SCO on limestone. The systems were also characterized by FTIR, TG/DTG, XRD, XRF, SEM, and zeta potential.

Influence of Mn precursor on pre-pyrolysis modification of sugarcane bagasse biochar for enhanced removal of 2,4-dichlorophenoxyacetic acid from aqueous solutions: Experimental and theoretical insights

Biochars impregnated with Mn oxides were produced using sugarcane bagasse (SB) modified with MnCl2 (Mn(II)-BC) or KMnO4 (Mn(VII)-BC) for the removal of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) through adsorption. The composites were structurally and functionally characterized by various techniques, revealing an irregular surface with oxide microspheres. Elemental analyses showed the presence of manganese and oxygen in distinct proportions. X-ray diffraction identified crystalline planes of MnO and Mn3O4, as well as the amorphous carbon phase. Infrared spectroscopy confirmed Mn bonded to oxygen, and its influence on BC graphitization was corroborated by Raman spectroscopy. Thermogravimetry highlighted the oxides' influence on thermal stability, while the total number of acidic and basic functions revealed notable differences in surface chemistry. Adsorptive removal of 2,4-D was optimized under conditions of pH 2.00, dosage of 2 g L−1, and particle size smaller than 100 mesh. Adsorption equilibrium was attained after 24 and 12 hours for Mn(II)-BC and Mn(VII)-BC, respectively, with experimental maximum capacities of 36.78 and 57.19 mg g−1. Freundlich and Sips isotherms fit better for Mn(II)-BC and Mn(VII)-BC, respectively, while Elovich and pseudo-second-order kinetic models were suitable. Density Functional Theory (DFT) calculations confirm that, with decreasing pH, hydrogen bonding takes place. At higher pH,binding with Mn3O4 suggests efficacy in Mn(II)-BC composite adsorption, not observed in Mn(VII)-BC due to an additional oxide, differentiating available sites. Despite Mn leaching challenges, post-acid exposure reuse showed favorable removal percentages, indicating potential for reutilization. These findings confirm the suitability of the synthesized composites as adsorbents for the remediation of water contaminated with 2,4-D.

Highly Porous Cellulose-Based Carbon Fibers as Effective Adsorbents for Chlorpyrifos Removal: Insights and Applications

The extensive utilization of the organophosphate pesticide chlorpyrifos, combined with its acute neurotoxicity, necessitates the development of effective strategies for its environmental removal. While numerous methods have been explored for chlorpyrifos removal from water, adsorption is the most promising. We investigated the potential of two cellulose-derived porous carbons as adsorbents for chlorpyrifos removal from water, prepared by either CO2 or H2O activation, resulting in similar morphologies and porosities but different amounts of heteroatom functionalities. The kinetics of batch adsorption removal from water fits well with the pseudo-first-order and pseudo-second-order kinetic models for both materials. The Freundlich, Langmuir, Dubinin–Radushkevich, and Sips isotherm models described the process of chlorpyrifos adsorption very well in all investigated cases. The maximum adsorption capacity determined from the Sips isotherm model gave values of 80.8 ± 0.1 mg g−1 and 132 ± 3 mg g−1 for the H2O and CO2 activated samples, respectively, reflecting the samples’ differences in heteroatom functionalities. Additionally, the application of either adsorbent led to reduced toxicity levels in all tested samples, implying that no harmful by-products were generated during adsorption. Comparative analysis with the existing literature further validates the study’s findings, suggesting the efficacy and applicability of cellulose-based porous carbons for sustainable chlorpyrifos remediation.

Dual-responsive drug carrier based on zeolitic imidazolate framework-8 incorporated into gold nanoparticles/chitosan/copper sulfide for controlled drug delivery

Currently, two major obstacles in effective treatment of breast cancer are development of resistance to chemotherapeutic drugs by cancer cells and the off-target cytotoxicity of these drugs. The main aim of this study was to synthesize a dual responsive nanocarrier by incorporating the zeolitic-imidazolate framework-8 into the gold nanoparticles/chitosan/copper sulfide for controlled release of doxorubicin. The prepared nanocarrier was characterized using various techniques, including Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, X-ray diffraction, and zeta potentials. The optimum experimental conditions, including adsorbent dosage (0.01–0.03 g), pH of solutions (5–9), contact time (5–15 min), and temperature (25–45 °C) at three levels were studied using the central composite design based on the response surface methodology. Our results indicated highest response (99 %) with 0.03 g of nanocarrier, at pH of 5, time of 10 min, and temperature of 35 °C. The obtained data were further studied with seven isotherm models. Based on the lower error sum of square values (0.059–0.514) and higher correlation coefficient values (0.9857–0.9972), Langmuir and Sips isotherm models were observed to be the best fitted. The in-vitro drug release study indicated 37.97 % of the drug being released in the simulated environment with physiological conditions, while 71.29 % of the drug was released in the simulated cancer cells condition at higher temperature. This data confirms the pH and temperature sensitivity of the nanocarrier. Enhanced drug release from the nanocarrier indicated low cell viability in the breast cancer cell line (MCF-7) under near-infrared laser irradiation. The IC50 values of nanocarrier and pure drug in MCF-7 cells were 243.95 and 4.442 μg L−1, respectively. Based on these data, we are concluding that our dual responsive nanocarrier has the potential to overcome the problems development of resistance of cancer cells and toxicity associated with current treatment of breast cancer.

Efficient uranium sequestration ability and mechanism of live and inactivated strain of Streptomyces sp. HX-1 isolated from uranium wastewater

Prokaryotes are effective biosorbents for the recovery of uranium and other heavy metals. However, the potential mechanism of uranium bioaccumulation by filamentous strain (actinobacteria) remains unclear. This study demonstrates the potential for and mechanism of uranium bioaccumulation by living (L-SS) and inactivated (I-SS) Streptomyces sp. HX-1 isolated from uranium mine waste streams. Uranium accumulation experiments showed that L-SS and I-SS had efficient uranium adsorption potentials, with removal rates of 92.93 and 97.42%, respectively. Kinetic and equilibrium data indicated that the bioaccumulation process was consistent with the pseudo-second-order kinetic, Langmuir, and Sips isotherm models. FTIR indicated that the main functional groups of L-SS and I-SS binding uranium were uranyl, carboxyl, and phosphate groups. Moreover, the results of XRD, XPS, SEM-EDS, and TEM-EDS analyses revealed for the first time that L-SS has biomineralization and bioreduction capacity against uranium. L-SS mineralize U(VI) into NH4UO2PO4 and CaU(PO4)2∙1.5H2O through the metabolic activity of biological enzymes (phosphatases). In summary, Streptomyces sp. HX-1 is a novel and efficient uranium-fixing biosorbent for the treatment of uranium-contaminated wastewater.

Biochar/Delonix regia seed gum/chitosan composite as efficient adsorbent for the elimination of phenol from aqueous medium

In this study, biochar (BC) from Delonix regia pods peel and gum from Delonix regia seed (SG) were prepared, and also biochar/chitosan composite (BCS) and biochar/Delonix regia seed gum/chitosan composite (BCGS) were fabricated for the efficient adsorption of phenol. Various characterization tools such as SEM, TEM, ATR-FTIR, TGA, zeta potential, and textural investigation were studied to examine the features of the synthetized adsorbents, confirming their positive construction. It was fully studied how necessary factors, comprising pH, dose of adsorbent, contact shaking time, initial phenol concentration, and temperature influenced adsorption behavior. An obvious rise of the adsorption capacity from 60.16 to 165.20 mg/g was achieved by the modification of biochar with Delonix regia seed gum and chitosan under ideal circumstances of 2 h contact duration, pH 7, 15 °C, and a dose of 2.0 g/L. The phenol adsorption was well applied by Langmuir, Temkin, Dubinin-Radushkevich, and Sips isotherms, in addition to nonlinear pseudo-second-order kinetic model. Furthermore, the physisorption, endothermic, and spontaneous process was illustrated by thermodynamic investigation. Additionally, the fabricated adsorbents could be effectively used and regenerated without main losses of only 7.5, 4.6, and 4.0 % for BC, BCS, and BCGS, respectively in the removal percentage after seven cycles of application.

Investigation of Kinetic, Equilibrium, and Thermodynamic Modeling of Perfluorooctanoic Acid (PFOA) Adsorption in the Presence of Natural Organic Matter (NOM) by Dielectric Barrier Discharge Plasma-Modified Granular Activated Carbon (GAC)

Perfluorooctanoic acid (PFOA) contamination in water sources poses significant environmental and health concerns. The kinetic, equilibrium, and thermodynamic features of PFOA adsorption in the existence of natural organic matter (NOM) were thoroughly investigated in this work using granular activated carbon (GAC) modified by dielectric barrier discharge (DBD) plasma. The impacts of DBD plasma parameters on the adsorption process were systematically examined. The results demonstrated that GAC modified by DBD plasma exhibited enhanced adsorption performance for PFOA, even in the presence of NOM. The optimal condition for plasma-treated GAC was achieved with 20 min of plasma treatment time and 100 W of plasma power, resulting in 92% PFOA removal efficiency in deionized water (DIW) and 97% removal efficiency in Chao Phraya River water (CPRW). A kinetic investigation using the pseudo-first-order model (PFOM), the pseudo-second-order model (PSOM), and the Elovich model (EM) indicated that plasma treatment time and NOM presence influenced the adsorption capacity and rate constants of PFOA with the PSOM having emerged as the most fitting kinetic model. The Langmuir isotherm model indicates monolayer adsorption of PFOA on plasma-treated GAC, with higher maximum adsorption capacity while NOM is present. The Redlich–Peterson and Sips isotherm models indicated varying adsorption capacity and heterogeneity in the adsorption system. The Sips model was determined as the most fitting isotherm model. Furthermore, the favorable and spontaneous character of PFOA adsorption onto plasma-treated GAC was validated by thermodynamic analysis, with endothermic heat absorption during the process. Overall, this comprehensive investigation provides valuable insights into the adsorption characteristics of PFOA in the existence of NOM using GAC modified by DBD plasma.

Green preparation of Fe3O4/HA/CS magnetic nanoparticles for oil–water separation

AbstractBACKGROUNDDemulsification using chitosan (CS)‐coated magnetic nanomaterials has garnered significant attention. However, traditional methods for synthesizing chitosan (CS)‐coated magnetic nanomaterials are often contaminated, laborious, and time‐consuming. Moreover, they showed poor demulsification efficiency due to the occupation of free amino groups in CS by crosslinking agents.RESULTSCS‐coated Fe3O4 magnetic nanoparticles (MNPs) were synthesized using humic acid (HA) as a bridge. The Fe3O4/HA/CS MNPs are recyclable demulsifiers for hexadecane‐water microemulsions. The impacts of MNP dosage, separation time, and pH on demulsification efficiency were studied comprehensively. Compared with Fe3O4/HA and Fe3O4/CS MNPs, the demulsification efficiency of the Fe3O4/HA/CS MNPs was superior. The pseudo‐second‐order kinetic model and the Sips isotherm best describe the demulsification process. Combined with the influence factors of demulsification efficiency, the demulsification mechanism involves electrostatic interactions between MNPs and oil microparticles. The maximum adsorption capacity for oil by the Fe3O4/HA/CS MNPs was 91.73 mg g−1.CONCLUSIONThis research presents a new method for connecting CS to MNPs with a high surface positive charge. As synthesized Fe3O4/HA/CS MNPs is expected to serve as highly efficient and recyclable demulsifiers for emulsified oil wastewater. © 2024 Society of Chemical Industry (SCI).

Unary adsorption of sulfonamide antibiotics onto pozzolan-tyre ash based geopolymers: Isotherms, kinetics and mechanisms

In this contribution, geopolymer composites, GP0, GP5-TA and GP10-TA, were prepared by alkaline activation and substituting pozzolan (Pz) with 0, 5 and 10 wt% of tyre ash (TA), respectively. The geopolymers were characterized using standard methods (XRD, TGA, FTIR, BET, SEM, Boehm titration and methylene blue and iodine indices) and were applied for the abatement of two sulfonamides, sulfamethoxazole (SMX) and sulfadimethoxine (SDM) in single-solute solutions. The effects of pH, salinity, initial concentration and contact time were evaluated. The incorporation of 5 and 10% TA increased the specific surface area (SSA) of pristine geopolymer (GP0) from 13.62 to 21.48 and 29.70 m2.g−1, respectively. The equilibrium data was best described by the Sips isotherm model. Salinity significantly diminished the adsorption of SMX and SDM. In aqueous medium, the geopolymers exhibited higher adsorption capacity for SDM (log Kow, 1.17) relative to SMX (log Kow, 0.86). In contrast, in saline medium, SMX uptake was higher, suggesting a cation-mediated adsorption. Adsorption of SMX was uncharacteristically independent of pH, whereas SDM uptake was significantly pH-dependent. The GP5-TA geopolymer composite exhibited the highest adsorption capacity for SMX in a saline environment (46.69 mg.g−1) and for SDM in non-saline water (107.69 mg.g−1). Adsorption rate was described by the pseudo-second order kinetic law. Adsorption mechanism was multi-mechanistic involving hydrophobic, ion exchange and charge assisted hydrogen bonding and electrostatic interactions in the case of SDM. Future works should optimize the functional groups density of active sites especially for sulfonamides in saline waters.

Efficient Removal of Water Soluble Fraction of Diesel Oil by Biochar Sorption Supported by Microbiological Degradation

The contamination of the water bodies by diesel oil (DO) and its water-soluble fraction (WSF) represents one of the most challenging tasks in the management of polluted water streams. This paper contains data related to the synthesis and characteristics of the plum stone biochar material (PmS-B), which was made from waste plum stones (PmS), along with its possible application in the sorption of the WSF of DO from contaminated water. Techniques applied in sample characterisation and comparisons were: Elemental Organic Analysis (EOA), Scanning Electron Microscopy−Energy Dispersive X-ray Spectroscopy (SEM-EDX), Fourier Transform Infrared Spectroscopy (FTIR), pH (pHsus) and point of zero charge (pHpzc). In order to increase the overall efficiency of the removal process, sorption and bioremediation were subsequently combined. Firstly, PmS-B was used as a sorbent of WSF, and then the remaining solution was additionally treated with a specific consortium of microorganisms. After the first treatment phase, the initial concentration of diesel WSF was reduced by more than 90%, where most of the aromatic components of DO were removed by sorption. The sorption equilibrium results were best fitted by the Sips isotherm model, where the maximum sorption capacity was found to be 40.72 mg/g. The rest of the hydrocarbon components that remained in the solution were further subjected to the biodegradation process by a consortium of microorganisms. Microbial degradation lasted 19 days and reduced the total diesel WSF concentration to 0.46 mg/L. In order to confirm the non-toxicity of the water sample after this two-stage treatment, eco-toxicity tests based on a microbial biosensor (Aliivibrio fischeri) were applied, confirming the high efficiency of the proposed method.

Sorption-enhanced intensified CO2 hydrogenation via reverse water–gas shift reaction: Kinetics and modelling

Intensification of CO2 hydrogenation via the reverse water–gas shift (RWGS) reaction for CO production can be achieved through in situ removal of water when hydrophilic adsorbents are incorporated alongside the catalyst in the reaction bed. In this work, seeking to move a step closer to the industrial implementation of this innovative CO2 valorization process, a comprehensive reactor model, validated by experimental data obtained in a fixed-bed reactor, was developed to simulate the behavior of this sorption-enhanced (SE) RWGS process. Simulation and experimental data matched with good accuracy, demonstrating the striking benefits brought by the adsorbent addition, such as an almost doubling of the CO production rate at 300 °C. The kinetics of RWGS reaction over a Cu-based catalyst and H2O adsorption on a 13X zeolite adsorbent were studied both experimentally and theoretically and the kinetic models were integrated into the reactor model to assess the performance of SE-RWGS process. Fitting of the RWGS reaction rates by a Langmuir-Hinschelwood-Hougen-Watson-type heterogeneous kinetic model suggested that the rate-determining step of the reaction is the surface interaction between an adsorbed CO2 molecule and a H* species on catalytic sites of different nature. Meanwhile, the dynamic behavior of water adsorption was effectively simulated by a semi-empirical double-stretched exponential model combined with the Sips isotherm model. The results of this work could be applied to the design and scale-up of the SE-RWGS process, which offers considerable improvements over the thermodynamically constrained conventional process. The intensified approach represents a promising avenue for the effective conversion of carbon dioxide into CO, as well as into other value-added chemicals as part of a multi-stage CO2 reduction process.

A novel sponge composite of chitosan-sodium tripolyphosphate-melamine for anionic dye Orange II removal

Since the potential carcinogenic, toxic and non-degradable dyes trigger serious environmental contamination by improper treatment, developing novel adsorbents remains a major challenge. A novel high efficiency and biopolymer-based environmental-friendly adsorbent, chitosan‑sodium tripolyphosphate-melamine sponge (CTS-STPP-MS) composite, was prepared for Orange II removing with chitosan as raw material, sodium tripolyphosphate as cross-linking agent. The composite was carefully characterized by SEM, EDS, FT-IR and XPS. The influence of crosslinking conditions, dosage, pH, initial concentration, contacting time and temperature on adsorption were tested through batch adsorption experiments. CTS-STPP-MS adsorption process was exothermic, spontaneous and agreed with Sips isotherm model accompanying the maximum adsorption capacity as 948 mg∙g−1 (pH = 3). Notably, the adsorption performance was outstanding for high concentration solutions, with a removal rate of 97 % in up to 2000 mg∙L−1 OII solution (100 mg sorbent dosage, 50 mL OII solution, pH = 3, 289.15 K). In addition, the adsorption efficiency yet remained 97.85 % after 5 repeated adsorption-desorption cycles. The driving force of adsorption was attributed to electrostatic attraction and hydrogen bonds which was proved by adsorption results coupled with XPS. Owing to the excellent properties of high-effective, environmental-friendly, easy to separate and regenerable, CTS-STPP-MS composite turned out to be a promising adsorbent in contamination treatment.

Metal organic framework composite based on CuBTC/SPION for application in methylene blue adsorption

AbstractIn this work, a composite (CuBTC/superparamagnetic iron oxide nanoparticles [SPION]) based on copper, benzene‐1,3,5‐tricarboxylic acid (CuBTC) and SPION was synthesized by electrochemical method for the magnetic separation of methylene blue (MB) from aqueous solutions. The synthesis of the proposed composite was carried out under various experimental conditions from 1.4 to 5.4 V for 1–5 h and subsequently studied using different techniques. Scanning electron microscopy showed a granular structure, whereas Brunauer–Emmett–Teller results revealed a well‐developed surface area of around 182 m2 g−1. Fourier transform infrared confirmed the presence of functional groups characteristic to CuBTC and Fe3O4, whereas X‐ray diffraction revealed the phase structure of CuBTC 1D, CuBTC 3D, and Fe3O4 in the obtained composite. Based on the experimental results, the sample synthesized under a potential of 1.4 V for 5 h was selected for MB adsorption studies in the function of adsorbent mass, contact time, solution pH, ionic strength, initial concentration, and temperature. The maximum adsorption capacity was 681 mg g−1, and the adsorption undergoes the Redlich–Peterson and Sips isotherm model. The results obtained for CuBTC/SPION indicate that the nanocomposite is a promising adsorbent for removing MB in synthetic dye water and wastewater.

Feasibility and sludge analysis of electrocoagulation process for Direct Violet-35 dye remediation

The present study investigates Direct Violet-35 (DV-35) remediation using electrocoagulation process. DV-35 which is an industrial azo dye, after release significantly affects the visual appearance of water bodies and hinders the process of photosynthesis affecting plant growth. Perturbing the food chain, it promotes toxicity, mutagenicity, and carcinogenicity. Therefore, dye remediation is essential before discharge into water streams. To determine the effectiveness of the electrocoagulation process for DV-35 dye remediation, and understand the influence of parameters like current density, inter-electrode spacing, concentration of electrolyte, pH, agitation speed, and initial dye concentration, a detailed study was carried out. Maximum removal efficiency (>98 %) was achieved in 16 min at 263.15 A/m2 current density and pH 7.2 for DV-35 concentration of 50 to 500 mg/L. Further, optimized parameters were applied to real textile effluent achieving 99.8 % efficiency. EC mechanism was corroborated by Sips isotherm matching adequately with experimental results. The findings also demonstrated a heterogeneous surface of the produced EC flocs. Pseudo-second-order was obtained with a low operating cost of 0.0018 US $/m3. The DV-35 removal and functional groups were confirmed by UV/VIS and Fourier transforms infrared spectroscopy analysis. The sludge was examined by X-ray Diffraction and Scanning Electron Microscope revealing Crystalline aluminum oxides i.e. bayerite (Al(OH)3) and diaspore (AlO(OH)). The conclusion of the results revealed EC to be an effective and economical technique for DV-35 remediation from textile wastewater.