Pseudo-second Order Kinetic Model Research Articles

Optimization of the Removal of Hexavalent Chromium Cr(VI) from Aqueous Solution by Moringa oleifera Bark-Derived Activated Carbon (MOBAC) Using Response Surface Methodology (RSM)

This study investigated the removal of hexavalent chromium Cr(VI) ions in an aqueous solution using Moringa oleifera bark-derived activated carbon (MOBAC). The adsorption removal of Cr(VI) was systematically investigated as a function of four experimental factors: pH (1-5), contact time (10-90 min), adsorbent dosage (0.020-0.100 g L-1), and temperature (25-45°C) by following a statistical experimental design. A response surface methodology (RSM)-based central composite experimental design was used to establish an empirical model that assessed factors' effects on Cr(VI) ions adsorptive removal. The model was verified and validated and used to predict optimal adsorption removal of Cr(VI) from aqueous solutions. At optimized conditions, 99.612 % of 1.5 mg L-1 Cr(VI) ions are removed from the aqueous solution. These optimum condition values include a pH of 2.1, contact time of 62.72 min, adsorbent dosage of 0.065 g L-1, and temperature of 39.8°C. The adsorptive mechanism was assessed by conducting isotherm and kinetic studies. The adsorption process of Cr(VI) ions by MOBAC is described by Langmuir isotherm, indicating monolayer adsorption, and the reaction kinetics is described by pseudo-second order kinetics model. The Langmuir monolayer adsorption capacity of Cr(VI) adsorption on MOBAC was found to be 4.577 mg g-1 for Cr(VI) ions. The findings support the use of MOBAC in the removal of Cr(VI) ions from aqueous systems.

Application of Activated Rice Husk for Adsorptive Bleaching of Groundnut Oil: Kinetic, Equilibrium and Thermodynamic Study

Kinetic, equilibrium and, thermodynamic studies of the bleaching of crude groundnut oil at optimized conditions were carried out using activated rice husk as an adsorbent for the bleaching process. The efficiency of bleaching was estimated by measuring the absorbance using a double- beam spectrophotometer at a wavelength of 450nm. The effects of adsorbent dosage, bleaching temperature and, contact time on the bleaching efficiency were studied. A directly proportional relationship was found between dosage and contact time and the bleaching efficiency while a bell curve was discovered for temperature increase. The surface area of the rice husk increased from
 150.32 to 1450.32 m2/g while the pore volume decreased from 0.15524 to 0.12844 cm3/g after activation which was determined via a Brunauer-Emmet-Teller (BET) analysis and the results further validated by the Scanning Electron Microscopy (SEM) images obtained. The kinetic data of the bleaching process were best described by the pseudo-second order kinetic model while the equilibrium adsorption isotherm analysis showed that the results from the Temkin isotherm were the most significant. The thermodynamic study revealed that the adsorptive bleaching process is feasible, spontaneous and, exothermic with a decrease in entropy. The enthalpy value also showed that the adsorption process is predominantly physisorption. This study has revealed that an effective adsorbent can be produced from rice husks under optimized process conditions.

Dual-functional Polyvinylidene Fluoride Beta Cyclodextrin-Grafted Graphene Oxide Mixed Matrix Membranes for Removal of Anionic Azo Dyes

AbstractMixed matrix PVDF polymeric membranes were incorporated with β–CD grafted graphene oxide (GO) nanocomposites (β–CD-g-GO) via nonsolvent induced phase separation method and used in the adsorption of congo red (CR) and methyl orange (MO) dyes. The incorporation of β–CD-g-GO (6 wt%) was found to improve the membrane physico-chemical properties and performance. The water content was increased by 24.26%, contact angle reduced from 84.17 to 62.97° while flux increased from 12.42 to 275.03 L m−2 h−1 bar−1. The membranes were able to remove 100% of CR at pH 7 and 99.4% of the MO dye at pH 5 within 240 min. The adsorption kinetics and isotherms were well fitted to the pseudo second-order kinetic model and Freundlich isotherm model respectively. These results indicated that the adsorption of both dyes occurred via chemisorption and in a multilayer on a heterogeneous surface of the membranes. According to these findings, it was concluded that the adsorption mechanism was due to hydrogen bonding interactions between nitrogen and hydroxyl groups, inclusion complexation introduced by β–CD molecules and electrostatic interactions, between the negatively charged oxygen-containing groups of the membrane and the positively charged nitrogen and azo-linkages of the dye molecules. PVDF/β–CD-g-GO membranes have shown excellent adsorption efficiency towards azo dyes. This work indicates that the embedding of adsorptive GO-β–CD nanocomposites in PVDF membranes can remove anionic dyes from wastewater treatment.

A green process for extracting and purifying coconut mesocarp polyphenols

Coconut, as one of the main tropical economic crops, has high yield and high demand. Coconut mesocarp (CM) is the main waste in coconut production, causing resource waste and bulk pollution issues. In this study, a green process for extracting and purifying CM polyphenols was developed, which was beneficial for turning waste into treasure and saving resources. The process included a series of steam explosion (SE) assisted alkali extraction methods for the total phenolic content (TPC) of total phenols (CTP) and insoluble phenols (CIP) in CM and purification process of macroporous resin. These results showed after SE treatment at 123 °C for 5 min, the TPC of CTP and CIP increased to 558.57 mg GAE/g dw and 280.67 mg GAE/g dw, which was higher 9% and 17.8% than the untreated sample, respectively. After purification with LX-83, the TPC of purified CTP (P-CTP) and CIP (P-CIP) increased to 773.16 mg GAE/g dw and 542.83 mg GAE/g dw. Both Langmuir and Freundlich adsorption models could be used to describe the adsorption behaviors of CTP and CIP. They were influenced by multiple factors and belonged to a pseudo second-order kinetic model. Subsequently, the main compounds in P-CTP and P-CIP were the abundant catechin, epicatechin, caffeic acid, p-coumaric acid and 4-hydroxybenzoic acid by HPLC-MS analysis. These results provided a basis for the green extraction and purification process of CM polyphenols.

Computational and experimental assessment of efficient dye adsorption method from aqueous effluents by halloysite and palygorskite clay minerals.

The removal of dyes from effluents of textile industries represents a technological challenge, due to their significant environmental impact. The application of halloysite (Hal) and palygorskite (Pal) clay minerals as adsorbents for the removal of Congo red (CR) and methylene blue (MB) was evaluated in this work. The materials were applied both in natural and acid-treated forms, and characterized by XRD, XPS, SEM-EDS, FTIR, and N2 adsorption-desorption isotherm techniques to identify their properties and main active sites. The adsorbents showed potential to remove CR (> 98%) and MB (> 85%) within 180min, using 0.3g adsorbent and initial dye concentration of 250mg L-1. Semi-empirical quantum mechanical calculations (SQM) confirmed the interaction mechanism between dyes and the adsorbents via chemisorption (- 69.0kcalmol-1 < Eads < - 28.8kcalmol-1), which was further observed experimentally due to the high fit of adsorption data to pseudo-second order kinetic model (R2 > 0.99) and Langmuir isotherm (R2 > 0.98). The use of Pal and Hal to remove dyes was proven to be economically and environmentally viable for industrial application.

Adsorption of AR114 onto humic acid-modified Fe3O4 nanoparticles

In this study, Fe3O4 and humic acid-modified Fe3O4 (Fe3O4@HA) magnetic nanoparticles were synthesized and used for the removal of Acid Red 114 (AR114) dyestuff from aqueous. The batch adsorption method was used for the experiments. The magnetic nanoparticles, synthesised by an inexpensive and environmentally friendly precipitation process, were characterised by FTIR, SEM-EDX, BET surface area, and XRD analyses. The optimum pH values determined for Fe3O4 and Fe 3O4@HA were the original pH (6.4) and 4, respectively. The equilibrium state was reached after 60 minutes for both adsorbents. The values for Fe 3O4 and Fe3O4@HA were determined as 3.4 mg/g and 3.1 mg/g, respectively, when 10 mg/l initial dyestuff concentration and 2 g adsorbent were used. The results obtained in the adsorption experiments performed for both adsorbents were compatible with the Freundlich isotherm and pseudo- second-order kinetic model. Fe3O4 was found to be more efficient than Fe3O4@HA in terms of reuse and Fe3O4 can be used 5 times without any significant loss of adsorption capacity. The results showed that Fe3O4 and Fe3O4@HA can be environmentally friendly alternative adsorbents for the removal of hazardous azo dyestuffs from water, and have regeneration possibilities.

Adsorption of Cu(II) from Aqueous Solution on Sonicated Activated Carbon Prepared from Arenga Pinnata Merr Fruit Shell Waste: Isotherm, Kinetic and Thermodynamic Studies

Adsorption of Cu(II) from aqueous solution on the activated carbon (AC) prepared from Arenga pinnata Merr fruit shell (APMFS) waste with the assistance of ultrasound was evaluated by conducting batch mode experiments. As a result, KOH activation using 40 kHz of ultrasound restructured active binding sites and produced more pores on the APMFS-AC according to FT-IR and SEM analyses, respectively. Increasing the sonication time from 45 min to 135 min increased the adsorption capacity from 6.535 mg/g to 7.042 mg/g, respectively, at the initial Cu(II) concentration of 257.213 mg/L, 27°C and pH 5. With an increment of the adsorption temperature to 45°C, it increased the adsorption capacity up to 11.765 mg/g. The investigation on the independent variables showed the optimum conditions of adsorption which were 257.213 mg/L of the initial Cu(II) concentration, 60 min of contact time, pH 5 and 45°C using 135 min of sonicated APMFS-AC. The Cu(II) adsorption isotherm was fitted with the Langmuir model at the optimum condition. The Langmuir mono-layer adsorption capacity obtained was 11.765 mg/g with the BET saturation capacity, and the total pore volume values were 13.029 mg/g and 3.987 L/mg, respectively. The Cu(II) adsorption followed the pseudo second-order kinetics model with the adsorption rate 0.473 g/mg.min. Thermodynamic parameters of enthalpy change (∆H0, 27.035 kJ/mol), Gibbs free energy (∆G0, 7.292 kJ/mol), entropy change (∆S0, 0.062 kJ/mol.K), and activation energy (E, 22.637 kJ/mol) were determined. These results confirmed that endothermic, spontaneous and chemical adsorption took place.

Highly efficient adsorption of ciprofloxacin from aqueous solutions by waste cation exchange resin-based activated carbons: Performance, mechanism, and theoretical calculation

This study focused on the preparation of a highly efficient activated carbon adsorbent from waste cation exchange resins through one-step carbonization to remove ciprofloxacin (CIP) from aqueous solutions. Scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectrometry, and X-ray photoelectron spectroscopy were used to characterize the physicochemical properties of the carbonized materials. The CIP removal efficiency, influencing factors, and adsorption mechanisms of CIP on the carbonized resins were investigated. Density functional theory (DFT) computations were performed to elucidate the adsorption mechanisms. The CIP removal reached 93 % when the adsorbent dosage was 300 mg/L at 25 °C. The adsorption capacity of the carbonized resins to CIP gradually decreased with an increasing pH from 3.0 to 7.0 and sharply declined with a pH from 7.0 to 11.0. The adsorption process better fitted by the pseudo second-order kinetic and Langmuir models, indicating that the interaction between CIP and the carbonized resins was monolayer adsorption. The maximum adsorption capacity fitted by the Langmuir model was 384.4 mg/g at 25 °C. Microstructural analysis showed that the adsorption of CIP on the carbonized resins was a joint effect of H-bonding, ion exchange, and graphite-N adsorption. Computational results signified the strong H-bonding and ion exchange interactions existed between CIP and carbonized resins. The high adsorption and reusability suggest that waste cation exchange resin-based activated carbons can be used as an effective and reusable adsorbent for removing CIP from aqueous solutions.

Photothermal self-floating aerogels based on chitosan functionalized with polydopamine and carbon nanotubes for removal of arsenic from wastewater

Although wastewater disposal in evaporation ponds may be a cost-effective strategy for wastewater management, it overlooks water recycling and can possibly pose significant threats to the surrounding environment. The development of photothermal materials with functional groups capable of adsorbing toxic contaminants offers a promising opportunity for detoxification and potentially solar-driven recycling of wastewater disposed in evaporation ponds. In this study, ultralight aerogels based on chitosan (Ch), a natural biodegradable polymer, functionalized with mussel-inspired polydopamine (PDA) and carbon nanotubes (CNT) were fabricated through a facile approach and examined for the removal of arsenic from water. Three aerogels, namely chitosan, CNT/Ch, and PDA@CNT/Ch were fabricated and characterized using SEM, FTIR, TGA, XPS, and BET surface area analysis. Adsorption isotherms, thermodynamics, and kinetics were systematically investigated, revealing the feasibility of the fabricated aerogels for arsenic removal from aqueous solutions. The UV–Vis and photothermal analysis indicated excellent light-absorption and light-to-heat conversion performance of the functionalized aerogels. Arsenic adsorption by aerogels occurred rapidly and reached equilibrium within 30 to 60 min and was well-fitted by pseudo second-order kinetics model. The Langmuir model well described the adsorption isotherm, and the maximum adsorption capacities were found to be 31.5, 36.6, and 38.7 mg/g at neutral pH for chitosan, CNT/Ch, and PDA@CNT/Ch, respectively. The adsorption mechanism was studied by FTIR and XPS analysis and the adsorption pathway was evaluated using intraparticle diffusion model. This study broadens the scope of utilizing aerogels for the detoxification and potential recycling of wastewater from diverse sources and effluents disposed in evaporation ponds.

Fe3S4 intercalated alkalized MXenes to enhancement of Au(III) and Cr(VI) removal by reduction and immobilization synergistic effect

Herein, Fe3S4 particles were introduced into an alkalized-Nb2CTx MXenes to construct Fe3S4@Alk-Nb2CTx composite for simultaneous reduction-immobilization of Au(III)/Cr(VI) from water aqueous. Spectrum analysis revealed that the –OH groups on the Alk-Nb2CTx surface assisted improving the dispersion and stability of Fe3S4, resulting in a favorable morphology and structure. The synthesized composites exhibited superior adsorptive property with a maximum adsorption values for Au(III) (2544.3 mg/g) and Cr(VI) (204.8 mg/g). Meanwhile, the removal of targeted pollutants on Fe3S4@Alk-Nb2CTx followed Pseudo-second order kinetics model and showed a good fit with the Langmuir isotherm model, indicating the nature of monolayer chemisorption. Besides, high adsorption selectivity of Fe3S4@Alk-Nb2CTx was still observed in the presence of interference ions, and it could be separated conveniently from solution by a magnet. More importantly, the model-fitting and characterization results manifested that high-density Fe, S and O groups were the main active factors in the as-prepared adsorbents, while the electrostatic attraction, complexation, redox and precipitation dominated the adsorption process. Hence, Fe3S4@Alk-Nb2CTx was a promising candidate employed for in situ environmental pollution incidents, especially competent for the reduction and removal of Au(III)/Cr(VI).

Hydrogel beads based on sodium alginate and quince seed nanoparticles for the adsorption of methylene blue

In this paper, bioadsorbents containing sodium alginate and quince seed nanoparticles were prepared using the ionotropic gelation method for the adsorption of methylene blue. The structural characterization of the bioadsorbents and nanoparticles was performed by using Fourier Transform-Infrared Spectroscopy (FT-IR), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), thermogravimetric (TG), and Brunauer-Emmett-Teller (BET) analysis. Cationic dye (methylene blue, MB) was used for the adsorption studies and some operational parameters such as initial pH solution, temperature, contact time, initial dye concentration, and adsorbent dose were optimized. The pseudo-first, and second order kinetics, Langmuir, and Freundlich isotherm models were used to analysis of the experiment results. The findings showed that the experimental results were fitted to the pseudo-second order kinetic and Langmuir isotherm models. The highest methylene blue adsorption capacity was obtained as 192.3 mg/g at 60 °C in the presence of sodium alginate bioadsorbent containing 5.0% quince seed nanoparticles at pH 7. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also calculated, and the MB adsorption on the bioadsorbents was performed as spontaneous and exothermic due to the negative value of the ΔG° and ΔH°.

Amine-functionalized single-layered 2D nanosheets of α-zirconium phosphate for highly efficient removal of Pb2+ ions and Congo red dye

This paper reports a facile route for preparing single-layered and crystalline 2D nanosheets of α-zirconium phosphate (α-ZrP), which were further functionalized through covalent attachment of amino organosilane on its exfoliated surfaces (AF-ZrP) to enhance their sorption capacity for Pb2+ and Congo red removal. Two possible surface arrangements of NH2 groups were observed: one as free amine groups without bonding and the other as protonated or hydrogen-bonded amine groups. AF-ZrP exhibits extraordinary adsorption capacities of 1640 and 1213 mg g−1 for removing Pb2+ ions and CR dye. Further, linear and non-linear regression methods have been studied and compared for fitting four adsorption isotherm models and two kinetics models. Non-linear Freundlich isotherm and non-linear pseudo-second order kinetic models prove the most suitable. The high adsorption capacity, easy regeneration, and reusability rendered AF-ZrP a suitable adsorbent for removing Pb2+ ions and Congo red (CR) dye at industrial scale.

Biogenic synthesis of iron oxide nanoparticles and experimental modeling studies on the removal of heavy metals from wastewater

Water pollution is a major global challenge due to the fast expansion of industrial activities and the increasing human population. Certain heavy metals can be exceedingly hazardous and contribute significantly to water contamination. In this study, iron oxide nanoparticles (IONPs) were synthesized using cyanobacteria extract to remove heavy metals (Cd and Pb) from the wastewater. To characterize the IONPs, several analytical techniques were employed such as Ultraviolet–visible spectroscopy revealed a SPR (surface plasmon resonance) peak at 348 nm and FTIR (Fourier transform infrared) spectral analysis showed the OH, C–H and S=O functional groups which confirmed the biomolecules responsible for the biogenic synthesis and stability. The surface morphology of the biogenic IONPs was investigated using SEM (scanning electron microscopy) which reveled their nearly spherical or cubic shape. Additionally, XRD (X-ray diffraction) analysis confirmed the crystallinity of IONPs, with a crystalline size measuring 18.21 nm. Effects of contact time, pH, initial metal ions concentrations, and IONPs dosage were studied on the adsorption of Cd and Pb ions. Different adsorption kinetics and isotherm models were applied to the experimental data. Pseudo second-order kinetic and Langmuir isotherm models were well fitted to the adsorption of Cd and Pb onto the IONPs. Higher correlation coefficients (R2) values of Langmuir isotherm (R2: 0.990 for Cd and Pb adsorption) and Pseudo second-order kinetic (R2: 0.998 and 0.999 for Cd and Pb adsorption, respectively) were found, which indicated the favorable interaction between the metal ions and adsorbent. Langmuir isotherm calculated maximal adsorption capacities of 105.932 and 118.764 mg/g for Cd and Pb, respectively. Recyclability of IONPs was conducted and after five adsorption/desorption cycles, IONPs retained their adsorption efficiency with negligible decline. After five cycles, IONPs removal efficiency was up to 80.41 and 88.35 % for Cd and Pb, respectively. Results of this study indicate that cyanobacteria-mediated IONPs were efficient adsorbent for Pb and Cd removal from contaminated aqueous solution.

Modelling and optimization of bovine serum albumin adsorption on calcium bentonite using box-behnken experimental design method

The purpose of this study is to investigate and optimize the process parameters for bovine serum albumin (BSA) adsorption onto calcium bentonite (CaB) using the Box-Behnken experimental design method. Calcium bentonite was characterized using FT-IR, SEM, XRD, zeta potential measurements, and Boehm titration methods. The BSA adsorption capacity of calcium bentonite was modelled with respect to pH (2.8, 4.8, and 6.8), temperature (25 °C, 32.5 °C, and 40 °C), and initial protein concentration (0.1–1.2 mg ml−1) using the Box-Behnken experimental design method. The Design Expert 13.0 software was used to optimize the process conditions and obtain three-dimensional response surface graphs. A regression model, which gives the relationship between the process parameters and BSA adsorption capacity, was obtained using Design Expert software. The developed model showed that the most effective parameter on adsorption was the initial protein concentration followed by pH and temperature. The maximum adsorption capacity was obtained about 171 mg/g under optimal conditions (pH 4.8, 40 °C, and 1 mg ml−1 of initial BSA concentration). BSA adsorption onto CaB fit the pseudo-second order kinetic model. This study showed that process parameters for BSA adsorption can be effectively investigated and optimized using the Box-Behnken experimental design method with a fewer number of experiments.

Dyeing sludge-derived biochar for efficient removal of antibiotic from water

Adsorption is one of the most effective methods for ecotoxic antibiotics removal, while developing high-performance adsorbents with excellent adsorption capacity is indispensable. As the unavoidable by-product of wastewater, sewage sludge has dual properties of pollution and resources. In this study, dyeing sludge waste was converted to biochar by KOH activation and pyrolysis, and used as an efficient adsorbent for aqueous antibiotics removal. The optimized dyeing sludge-derived biochar (KSC-8) has excellent specific surface area (1178.4 m2/g) and the adsorption capacity for tetracycline (TC) could reach up to 1081.3 mg/g, which is four and five times higher than those without activation, respectively. The PSO (pseudo-second-order) kinetic model and the Langmuir isotherm model fitted better to the experimental data. The obtained KSC-8 has stabilized adsorption capacity for long-term fixed-bed experiments, and maintained 86.35% TC removal efficiency after five adsorption-regeneration cycles. The adsorption mechanism involves electrostatic attraction, hydrogen bonding, π-π interactions and pore filling. This work is a green and eco-friendly way as converting the waste to treat waste in aiming of simultaneous removal of antibiotics and resource recovery of dyeing sludge.

Phosphorus-enriched biochar from biogas residue of Eichhornia crassipes: transformation and release of phosphorus

Pyrolysis is an effective technology for treating and utilizing biogas residue. To explore the phosphorus (P) supply capacity of the biochar generated from biogas residue of Eichhornia Crassipes, the P speciation of E. crassipes biogas residue and biomass during pyrolysis (300–700 °C) was analyzed by combining sequential chemical extraction, 31P nuclear magnetic resonance (NMR) and P K-edge X-ray absorption near edge structure (XANES) spectroscopy. Pyrolysis treatment promoted the conversion of amorphous Ca-P phases in biogas residue and biomass into crystalline hydroxyapatite (HAP) phase, which matched the formation of stable HCl-P pools in the biochar derived from biogas residue (AEBs, 22.65–82.04%) and biomass (EBs, 13.08–33.52%) in the process of pyrolysis. Moreover, the total P contents in AEBs (19.43–28.92 mg g−1) were higher than that of EBs (3.41–5.26 mg g−1), indicating that AEBs had a great P reclamation potential. The P release kinetics from AEBs and EBs in water were evaluated via an incubation experiment for 360 h. The P release from both AEBs and EBs conformed to the pseudo-second order kinetics model (R2 > 0.93), but their P release behaviors were different. The P release of AEBs conformed to the diffusion-re-adsorption model, while that of EBs accorded with the diffusion-dissolution model. The diffusive gradients in thin-films (DGT) analysis showed that AEBs could significantly increase soil available P content as compared with EBs. Hence, the biochar produced from biogas residue of E. crassipes via pyrolysis has a good application potential as a P fertilizer.Graphical

The implementation of ZnS–SnS BM NPs for phenanthrene degradation: An adsorptive photocatalyst approach and its toxicity studies in adult zebrafish

Phenanthrene is a persistent organic pollutant released by numerous industries. The purpose of the study is to construct a batch reactor for phenanthrene degradation using a bimetallic (BM) ZnS–SnS nanoparticle as a photocatalyst. ZnS–SnS BM NPs were used as a photocatalyst, employed from precursors Zinc acetate dihydrate and tin (II) chloride dihydrate, with crystalline cubic-shaped particle sizes. ZnS–SnS BM NPs were utilized in batch adsorption assays to assess the impact of phenanthrene degradation parameters on various PAHs (Polycyclic aromatic hydrocarbons) concentrations, pH levels, and irradiation sources. Adsorption kinetic and isotherm tests revealed that the pseudo-first order kinetic model, pseudo-second order kinetic model, and Langmuir isotherm model all fit effectively with the effective phenanthrene degradation using ZnS–SnS BM NPs. The degraded product were analyzed for GC-MS, revealing that organic pollutant phenanthrene was converted into harmless by-products like n-hexadecenoic acid, oleic acid, and octadecanoic acid. The toxicity of phenanthrene was observed to decrease with an increase in ZnS–SnS BM NPs concentration. ZnS–SnS BM NP concentration of 150 μg/mL, the zone of inhibition values was recorded highest zone of inhibition (19 ± 1.2 mm) against the strains S. epidermis followed by B. cereus and Clostridium spp. Further adult zebrafish were found to be less toxic to ZnS–SnS BM NPs after 96 h of exposure, with an LD50 of 100 μg/L. The toxicity escalated as concentrations increased. Behavior test showed normal swimming, learning, and memory in open tank and T-maze tests, while 100 μg/L showed pausing/frozen time in zebra fish therefore low doses are considered safe. Hence by employing ZnS–SnS BM NPs can be engaged in waste water treatment for PAH degradation.

Preparation and characterization of γ-AlOOH/Fe3O4 for the highly effective removal of Congo red from wastewater

Due to the highly toxic and non-degradable nature of Congo red (CR) in wastewater, how to effectively separate CR from an aqueous solution remains a major challenge in the field of wastewater treatment. Consequently, an γ-AlOOH/Fe3O4 composite was prepared using the sol-gel method under ultrasonic stirring conditions. The structural and surface properties of the magnetic γ-AlOOH/Fe3O4 composite were analyzed in detail using a range of physical and chemical characterization methods. It was shown that the γ-AlOOH/Fe3O4 composite possessed the advantages of its layered structure, high porosity, and positively charged surface, all of which were conducive to improving the adsorption capacity of CR. During our CR adsorption experiments, the maximum adsorption amount reached 1350.11 mg g−1. Simultaneously, the whole adsorption process was more consistent with the pseudo-second order kinetic and Langmuir isotherm model. The adsorption activation energy and thermodynamic data prove that the adsorption process was chemisorption, spontaneous, and endothermic. In addition, the γ-AlOOH/Fe3O4 composite can be easily separated from treated-wastewater upon the application of an external magnetic field and its excellent reproducibility increases its practical application value. Therefore, the γ-AlOOH/Fe3O4 composite synthesized in this study has a wide range of practical applications.

Adsorption of cobalt (II) ions from aqueous solution using cow bone and its derivatives: Kinetics, equilibrium and thermodynamic comparative studies

Mono-component adsorption of Co2+ ions from simulated industrial water was investigated by using cow bone (CB), cow bone char (CBC), and activated cow bone carbon (ACBC) adsorbents synthesized from raw cow bone as the precursor. The resulting prepared adsorbent materials were then characterized using analytical methods such as: zeta potential measurements, BET surface area, FTIR, SEM, EDS, and XRD analysis. For all synthesized adsorbents, the main compositions were mesopores with the presence of CC, PO32−, CO32 and O-H bonds signifying hydroxyapatite nature of the adsorbents. The isoelectric point (pHIEP) of ACBC was obtained to be 3.59 (lowest among the prepared adsorbents) thereby signifying that ACBC's electrostatic force of attraction was relatively higher between the Co2+ and its surface. The study showed that the pseudo second-order kinetic model had the best correlation for all the adsorption kinetic experimental data for each prepared adsorbent, inferring that the rate-controlling step during the Co2+ ions adsorption onto the prepared adsorbents is chemisorption. The Sips isotherm model excellently predicted the adsorption data for the adsorption of Co2+ ions on the CB adsorbents while the Langmuir isotherm best fitted the equilibrium data of the CBC, and ACBC prepared adsorbents with excellent correlation coefficients, while maximum adsorption capacities, qmax, were obtained to be 52.50, 58.80, and 64.50 mg g−1 for CB, CBC, and ACBC respectively. The study of the thermodynamic properties of the adsorption of Co2+ showed the process was endothermic, non-spontaneous and endogenic for the ACBC adsorbent, while being exothermic for the CB, and CBC adsorbents in addition to having physisorption properties.

Fabrication of Highly Efficient Fe3O4/SSIP/GO Composite Films for Removal of Methylene Blue Dye

In this paper, we report the preparation of a new Fe3O4/SSIP/GO composite film for the purification of methylene blue dye from solution media. The preparation process of composite film was carried out to improve the interaction between the inner part of the sunflower stalk (SSIP) and surface matrix using magnetite/Graphene Oxide (Fe3O4/GO) minerals at weight ratios (0.2/4/0.2:w/w/w). The characterizations of as-developed Fe3O4/SSIP/GO composite film was successfully carried out by some advanced techniques such as FT-IR, SEM, and TGA analyses. Adsorption kinetic studies were evaluated in three different aspects as a pseudo-first-order model, pseudo-second-order model, and intraparticle diffusion-type model. Based on the R2 results, it was seen that the Pseudo-second order kinetic model (0.999) acted more harmoniously than the pseudo-first-order (0.960) and intra-particle diffusion technique models (0.974). In the light of these findings, it can be said that the prepared Fe3O4/SSIP/GO composite film used for removal of methylene blue dye can be considered as a promising material