Pseudo 1st Order Research Articles

Biomass impregnated zero-valent Ag and Cu supported-catalyst: Evaluation in the reduction of nitrophenol and discoloration of dyes in aqueous medium

The stem part of the Melia Azadarach (MA) plant species was impregnated with Ag and Cu ions and subsequently reduced with NaBH4 in aqueous medium and were named as MA@Ag and MA@Cu. These nanocatalysts were characterized through FTIR, XRD, TGA, EDS and FESEM. Various analysis was performed to evaluate the inherent functional groups, crystallinity, thermal stability, elemental analysis and surface characteristics of the catalysts. Both catalysts were applied for the discoloration of dyes and reduction of PNP in the presence of NaBH4 in aqueous medium. Initially, both the catalysts were applied for the reduction of PNP (p-nitrophenol) and discoloration MO (methyl orange) dye. Pseudo-1st order kinetics was applied for calculating kapp and R2 values. The apparent rate constant (kapp) was highest for the discoloration reaction of RB (122.85 min-1) and MB (14.534 min-1) in which the catalyst was MA@Ag thus, indicating strongest catalytic activity. Similarly, 0.9574 and 0.9572 are the best-fitted adjacent R2 values obtained from MO and MB degradation using MA@Ag. Both the rate constant value and turnover frequency (TOF) indicated that MA@Ag exhibited higher activity.

Kinetic and optimization study of sustainable biodiesel production from waste cooking oil using novel heterogeneous solid base catalyst

The novel Na-SiO2@TiO2 heterogeneous base catalyst was designed and successfully applied to the trans-esterification reaction of waste cooking oil for sustainable biodiesel production. The designed catalyst was characterized by SEM, XPS, FT-IR and BET before treatment, illustrated its suitability for the catalytic trans-esterification reaction. Moreover, the influence of reaction temperature, time, catalyst concentration and WCO:MeOH molar ratio on the catalytic activity were also investigated, resultant 98% biodiesel yield was achieved. The reusability test demonstrated that the Na-SiO2@TiO2 catalyst has noticeable catalytic potency up to 5 successive runs. Besides, the kinetics study explains that the reaction is kinetically controlled by pseudo 1st order. The Ea was found to be 21.65 kJ/mol. Similarly, the important thermodynamic parameters such as ΔH#, ΔS# and ΔG# were estimated to be 18.52 kJ.mol−1, −219.17 J.mol−1K−1and 92.59 kJ.mol−1respectively.

Biocomposite hydrogel beads from glutaraldehyde-crosslinked phytochemicals in alginate for effective removal of methylene blue

Phytochemicals, i.e., flavonoids, phenolics, and anthocyanin, extracted from red cabbage, were crosslinked with alginate to prepare biocomposite hydrogel beads (BHB). The preparation of BHB involved three consecutive steps: (1) extraction and solvent reduction of phytochemicals from red cabbage, (2) crosslinking of phytochemicals into alginate matrix using glutaraldehyde, and (3) formation of the hydrogel beads in CaCl2 solution. The resulting BHB sorbents were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analyses. The cross-section structure of the BHB was confirmed from the SEM images. The alteration of FTIR peaks implied the success of the crosslinking of phytochemical compounds into the alginate. The adsorption equilibrium and kinetic studies of BHB were conducted using basic blue 9 (BB9) as the model adsorbate. FTIR characterization of the BHB post-adsorption reveals the functional groups of the adsorbent involved in the dye adsorption. The calculated adsorption isotherm, kinetics, and thermodynamic parameters show good agreement with the characterization results of adsorbate post-adsorption. The adsorption isotherm is being in congruence with the Langmuir model, and the highest adsorption capacity recorded was 1442.0 mg g−1 at 323 K and pH of 11.0. Adsorption kinetics was better fitted to the pseudo 1st order model than the pseudo 2nd order and Elovich models, which further support the dye physisorption behavior. The initial adsorption rate was influenced by the rapid surface adsorption followed by intraparticle diffusion. The thermodynamic parameters show the spontaneity of the adsorption, and the adsorption proceeds endothermically. The cost analysis shows the economic feasibility of BHB sorbent production for adsorption applications.

Insights into kinetics, isotherms and thermodynamics of phosphorus sorption onto nanoscale zero-valent iron

The main aim of this study is to investigate the suitability of several adsorption isotherms and kinetic models for describing the removal of phosphorus (P) from aqueous solutions by nanoscale zero-valent iron (NZVI). Removal efficiency was assessed through batch experiments using initial P-concentration ranged from 5 to 100 mg/L. Statistical error analysis was conducted to examine the validity of the applied models to interpret the removal process. Results showed that NZVI dosage of 1 g/L could remove up to 76.8 mg-P with 100 mg/L of P-initial concentration. Moreover, Langmuir isotherm and pseudo 2nd order kinetic model were the best models to describe the experimental data of P-sorption onto NZVI, with the highest linear and non-linear correlation (R2). Results suggested that chemisorption is the main mechanism involved in P-removal by NZVI in addition to the possibility of physical-electrostatic deposition of P-species onto the surface of NZVI within the liquid-solid controlling step. Functional error analysis quantitatively confirmed the applicability of the proposed isotherm and kinetic models in describing the P-sorption data. Akaike Information Criterion (AIC) values confirmed the goodness-of-fit of the Langmuir isotherm model, linear pseudo 2nd and 1st order models, and non-linear pseudo 1st order model to the experimental data. Thermodynamic analysis, with high enthalpy value of 67.87 kJ/mol, confirmed endothermic nature in the NZVI/P system and the involvement of physio/chemisorption process. The present insights into sorption and reaction rate analysis of P by NZVI revealed that it could have subsequently occurred on two main steps of liquid-film and liquid-solid diffusions.

Adsorption Evaluation for the Removal of Nickel, Mercury, and Barium Ions from Single-Component and Mixtures of Aqueous Solutions by Using an Optimized Biobased Chitosan Derivative.

In this experimental study, the use of 5-hydroxymethyl-furfural (HMF) organic compound as a grafting agent to chitosan natural polymer (CS) was examined. One optimized chitosan derivative was synthesized, and then tested (CS-HMF), in order to uptake nickel, mercury, and barium metal ions from single- and triple-component (multi-component) aqueous solutions. The characterization of the material before and after the metal uptake was achieved by scanning electron microscopy (SEM). The ability of the adsorption of CS-HMF was tested at pH = 6. The adjusting of temperature from 25 to 65 °C caused the increase in the adsorption capacity. The equilibrium data were fitted to the models of Langmuir and Freundlich, while the data from kinetic experiments were fitted to pseudo-1st and pseudo-2nd order models. The best fitting was achieved for the Langmuir model (higher R2). The adsorption capacity for nickel, mercury, and barium removal at 25 °C (single component) was 147, 107, and 64 (mg/g), respectively. However, the total adsorption capacity for the multi-component was 204 mg/g. A thermodynamic study was also done, and the values of ΔG0, ΔH0, and ΔS0 were evaluated.

A UIO-66/tannic acid/chitosan/polyethersulfone hybrid membrane-like adsorbent for the dynamic removal of dye and Cr (VI) from water

Abstract The water-soluble pollutant including dye and heavy metal was a challenge to the water and environment. Adsorption was among one of the most promising technique for the recycle of dye but it usually required a long contact time. A membrane-like adsorbent was fabricated by mixing and depositing tannic acid, chitosan and metal organic framework (MOF, UIO-66) on polyethersulfone (PES) membrane in this study. The material was dense enough to conduct filtration like a membrane to remove both the anionic and cationic dye (acid brilliant scarlet and methylene blue), as well as Cr(VI) from water. When the ratio of MOF/Chitosan was 30% and the pH for mixing was 3.5, the pollutant removal reached 99% in the filtration for 200 min. The adsorbent in the dynamic filtration showed a pollutant loading capacity 3 times of the capacity in the static adsorption, which was caused by the enhanced driving force brought by the concentration polarization in the filtration. The particle size of the TA/CS/MOF mixture were characterized by dynamic light scattering as well as Zeta potential, FTIR, XRD, TEM and XPS. The morphology of membrane was observed by SEM. The result showed that the MOF played as core to disperse the tannic acid-chitosan mixture to improve the pollutant removal. TEM showed the TA/CS mixture formed an uniform coating outside the MOF particle at the pH of 3.5. The pseudo 1st order and pseudo 2nd order model fitted the adsorption kinetics well, while the Elovich model did not fit very well.

Adsorptive removal of tetracycline and amoxicillin from aqueous solution by leached carbon black waste and chitosan-carbon composite beads

Carbon black waste as waste by-product of oil refineries, exhibits improved specific surface area and is rich in surface functional groups after leaching. In this work, both powdered leached carbon black waste (LCBW) and LCBW-chitosan composite beads prepared via instantaneous gelation method were utilized as adsorbent to study their adsorption capabilities and behaviors for removal of tetracycline (TC) and amoxicillin (Amox) in distilled and tap water. The characterization showed that LCBW is high in specific surface area (~375 m2/g) and contains carboxyl (‒COOH) and hydroxyl (‒OH) groups which are essential to the adsorption. Under the experimental conditions, adsorption capacities ranging from 12 to 205 mg/g were obtained. It was observed that the adsorption performance of powdered LCBW was enhanced by the cations presented in the tap water while the effect was insignificant to LCBW-chitosan beads. The kinetics studies showed that the adsorption of the studied antibiotics on powdered LCBW and composite beads fitted well with pseudo 1st-order and pseudo 2nd-order model, respectively. The fitting of intraparticle diffusion model showed that the adsorption process was not governed solely by intraparticle diffusion. LCBW-chitosan beads was used to investigate the continuous adsorption of TC in a fixed bed column and the experimental data was fitted to Adams-Bohart model and Thomas model.

Modelling the Effect of Nanoscale Zero-Valent Iron (nZVI), Biochar (BC) and Nanoscale Zero-Valent Iron/Biochar (nZVI/BC) on the Adsorption/Reduction of Nitrobenzene (NB)

In most instances, there exists an inaccuracy in interpretation of adsorption/reduction of substances using linear technique as it can only provide an approximate value of the measured parameter; the specific adsorption rate. This paper provides for the first-time modelling of the effect of nZVI/BC, nZVI and Biochar (BC) on the adsorption/reduction of nitrobenzene as modelled using Pseudo-1st order (PFO), Pseudo-2nd Order (PSO), Elovich and Avrami models. Pseudo-1st Order was the best model for nZVIBCg, whereas Pseudo-2nd Order was the best model for nZVI and BC on Nitrobenzene (NB) removal based on statistical dependencies that were used such as root-mean-squire error (RMSE), bias factor (BF), Akaike information criterion (AICc) and the adjusted coefficient of determination. Justifiably from the results, coupling nZVI and BC together will help in reducing more of NB than when individual compounds are used.

Test for Outlier and Normality of the Residuals for the Pseudo-1st Order Kinetic Modelling of Glyphosate Adsorption onto Palm Oil Fronds

Generally, in nonlinear regression, the residuals of the curve must be distributed normally, and residuals must be tested for the presence of outliers. This is normally done using normality tests such as the Kolmogorov-Smirnov, Wilks-Shapiro and D'Agostino-Pearson and the Grubb's test, the latter test for the presence of an outlier, which is the focus of this study. Normality tests for residues used in general nonlinear regression revealed that the usage of the pseudo-1st order model in the fitting of glyphosate biosorption to palm oil fronds was adequate due to lack of an outlier. The Grubb’s test was applied to the residual results. The critical value of Z from statistical table for Grubbs’ test for a single outlier using mean and SD was 2.289 (n=10). The Grubbs (Alpha = 0.05) g value was 1.844. As the test statistic is lesser than the critical assigned value, no outlier was deemed present.

Micellar and Transition Metal Ion Catalysed Oxidation of Pentanol in Aqueous Medium

Abstract Micelles and 4d- or 5d-transition metal ions have been proved to be effective catalysts for the oxidation of 1-pentanol by Ce(IV) in aqueous medium under pseudo 1st order reaction conditions at 258C. Although cationic micelles show a speed retarding effect, anionic SDS micelles accelerate the reaction rate. The Ir(III) and Ru(III) catalysed reactions show shorter half-lives at micromolar concentration. Active Ce(IV) species are also identified and an explanation of the different catalytic activities of metal ions and micelles is presented. The accumulation of the substrate in the Stern-layer of the SDS micelles is detected. The reaction product is confirmed by melting point analysis, a 2,4-DNP test, and by IR and NMR studies.

Adsorptive Removal of Basic Green Dye from Aqueous Solution Using Humic Acid Modified Magnetite Nanoparticles: Kinetics, Equilibrium and Thermodynamic Studies

In the present study humic acid modified magnetite (HA-Fe3O4) nanoparticles as a novel magnetic adsorbent was synthesized by in situ co-precipitation method for malachite green (MG) remediation. The physio-chemical properties of the prepared nanoparticles were fully examined by using FTIR, SEM–EDX, XRD and UV–Vis, analysis. The pHpzc, specific surface area and suspension stability in aqueous system of the synthesized Nps were also evaluated. The various characterization revealed that HA–Fe3O4 was effectively synthesized and HA effectively control aggregation and oxidation of Fe3O4 in aqueous system. The XRD result reveals that the synthesized materials have a crystal size of 9.17 and 11.21 nm for HA-Fe3O4 and Fe3O4 Nps respectively. The operational parameters on the removal of MG by the synthesized Nps were also evaluated. The temperature dependence data also revealed that MG sorption process was feasible, spontaneous and endothermic. The MG adsorption rates were described by the pseudo 1st order model and Freundlich isotherm model. The maximum adsorption monolayer capacity of HA-Fe3O4 and Fe3O4 was 79.3 mg/g and 62.2 mg/g respectively. The reusability is an important factor to evaluate the HA-Fe3O4 and Fe3O4 in real applications and the optimum desorption was attained at 0.1 M of HCl for both Nano-sorbents. Based upon the results, the prepared Nano sorbent could be efficient for the removal of different cationic dyes from waste water.

Comparative removal of two antibiotic resistant bacteria and genes by the simultaneous use of chlorine and UV irradiation (UV/chlorine): Influence of free radicals on gene degradation

The research aimed to remove antibiotic resistance by the simultaneous use of UV irradiation and chlorine (UV/chlorine). The inactivations of tetracycline resistant bacteria (TRB) during chlorination, UV irradiation, and UV/chlorine was investigated and compared with those of amoxicillin resistant bacteria (AmRB). Similar examination was also conducted for comparing the removals of their resistant genes (i.e., tetM and blaTem). The removals of antibiotic resistance highly depended on chlorine doses and UV intensities. The sufficient chlorine dose (20 mg.L−1) in the chlorination and the UV/chlorine completely inactivated TRB and AmRB (>7.3 log), while the UV irradiation could not achieve the complete disinfection. Microorganisms resistant to different antibiotics exhibit different susceptibility to the disinfection processes. The removals of antibiotic resistant genes (i.e., tetM and blaTem) were more difficult than those of TRB and AmRB. The UV/chlorine was the greatest process for tetM and blaTem removals, followed by chlorination and UV irradiation, respectively. Chlorination decreased the tetM and blaTem by 0.40–1.45 log and 1.04–2.45 log, respectively. The blaTem gene was highly reactive to chlorine, compared with tetM. The UV irradiation caused the tetM and blaTem reductions by 0.32–0.91 log and 0.59–0.96 log, respectively. The UV/chlorine improved the tetM and blaTem removals by 0.98–3.20 log and 1.28–3.36 log, respectively. The •OH contributed to the fraction of tetM and blaTem removals by 48% and 19%, respectively. The effect of reactive chlorine species on the tetM and blaTem removals was minor. The pseudo 1st-order kinetic constants (k′) for tetM and blaTem removals by the UV/chlorine were highest. The •OH enhanced the k′ values by 120% and 20% for the tetM and blaTem removals, respectively. The study showed the potential use of UV/chlorine for controlling antibiotic resistance.

Comparison between removal of Ethidium bromide and eosin by synthesized manganese (II) doped zinc (II) sulphide nanoparticles: kinetic, isotherms and thermodynamic studies.

The present work seeks to investigate the kinetics and thermodynamic studies of ethidium bromide (EtBr) and eosin adsorption onto the synthesized Manganese (II) doped Zinc (II) Sulphide nanoparticles. A convenient scheme of co-precipitation was used for the synthesis of Manganese (II) doped Zinc (II) Sulphide nanoparticles. The Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM) and X-ray diffractogram (XRD) techniques were used for the characterization of synthesized nanoparticles. The adsorption study was undertaken in a systematic manner. Effects of different experimental parameters were studied using batch adsorption method. It was evident from the results that EtBr and eosin removal was inversely proportional to the concentration of initial dye and directly proportional to contact time and adsorbent used. To study the adsorption equilibrium three different isotherm models like Langmuir, Freundlich and Flory-Huggins were used. It was observed that adsorption data synced most successfully with Langmuir isotherm model as compared to Freundlich and Flory-Huggins isotherm model. To fit the investigational statistics, the kinetic models pseudo 1st order, pseudo 2nd order and intra particle diffusion were taken onto consideration. The maximum dye removal of 98.19% and 97.16% for EtBr and eosin, was observed during the synthesis of nanoparticles.

Adsorption of lead(II) and chromium(VI) from aqueous environment onto metal-organic framework MIL-100(Fe): Synthesis, kinetics, equilibrium and thermodynamics

In present research, MIL-100(Fe) was efficiently synthesized by hydrothermal strategy applying HF as mineralizing agent and its ability was examined for lead(II) and chromium(VI) adsorption from an aqueous environment. Structural, chemical and morphological properties of the synthesized MOF were specified by different experimental techniques including XRD, FTIR, SEM, EDS and adsorption isotherms of N2 at 77 ​K (BET). D-spacing was measured with Debye–Scherrer’s formula as 7.98 ​Å. Also, the analyses confirmed relatively high BET surface area (1843.9 ​m2 ​g−1) and an octahedral-shaped structure for MIL-100(Fe) synthesized. Additionally, the adsorption behavior of lead(II) and chromium(VI) onto the MIL-100(Fe) was investigated using kinetics, equilibrium and thermodynamic parameters. Equilibrium analysis exhibited that the maximum uptake capacity for lead(II) was 23.46 ​mg ​g−1 based on sips model and for chromium(VI) was 30.45 ​mg ​g−1 ​by Langmuir isotherm. The sorption kinetics of lead(II) followed the pseudo 1st order model, while for chromium(VI) followed both pseudo 1st order and pseudo 2nd order models. Thermodynamic conclusions indicated a non-spontaneous nature for the sorption of each two metals and an exothermic reaction for lead(II) and endothermic nature for chromium(VI). Meanwhile, chemical ion-exchange and physisorption were distinguished as dominant adsorption mechanisms for lead(II) and chromium(VI), respectively.

Adsorption of amoxicillin onto high surface area-activated carbons based on olive biomass: kinetic and equilibrium studies.

This study presents the extraction of antibiotic amoxicillin (AMX) from aqueous solution employing activated carbons (AC) from olive biomass (OB). Two AC were prepared using ZnCl2 (activator agent), and a conventional muffle furnace (ACF) or microwave oven (ACMW). The structure, morphology, and textural properties from both AC were analyzed by scanning electron microscope (SEM), pH of point-zero-charge (pHPZC), infrared spectroscopy (FTIR), and N2 adsorption/desorption isotherms. AC with mesoporous structures rich in oxygenated groups and high specific area (as high as 1742 m2 g-1) were helpful for the efficient and fast adsorption of AMX. The Avrami kinetic nonlinear equation showed the best fitting for the empirical data when related to the pseudo-1st and pseudo-2nd order. The isothermal experimental data followed the Liu nonlinear model, displaying at 25 °C the maximum sorption capacity of 237.02 and 166.96 mg g-1 for the ACF and ACMW, respectively. An adsorption test with synthetic hospital effluent was carried out to evaluate the possibility of applying both adsorbents in wastewater purification. The purification efficiency was up to 94.4% and 91.96% for ACF and ACMW, respectively. Therefore, the AC obtained from OB (containing a mixture of seed, pulp, and olive peel) has a high potential for application in removing emerging contaminants from the wastewater.

Parametric optimization by Taguchi L9 approach towards biodiesel production from restaurant waste oil using Fe-supported anthill catalyst

Restaurant waste oil is easily obtainable from local restaurants, while anthills grow widely in Oro, Nigeria. The anthills were first carbonized, then steam activated to prepare an inert, porous support capable of functional group adsorption. The support was then doped with Fe (II) using FeSO4 and the Fe/A catalyst was used in biodiesel synthesis from the RWO. L9 Taguchi OA was chosen to optimize the transesterification proves parameters comprising of catalyst concentration, methanol to oil ratio, reaction temperature and reaction time. The optimization revealed that methanol concentration does not affect the biodiesel yield significantly, while reaction time has the highest contribution. A biodiesel yield of 99.73 % was attained at 60 °C for 1.5 h with 1.2 % catalyst and 6:1 methanol:oil ratio. GC analysis showed the product to be rich in methyl esters. Fuel characterization tests show that the product has properties exceeding the standards set by ASTM. Kinetic studies show the process adheres to pseudo 1st order kinetics and has high reaction rate and frequency factor (A) with low EA, while the catalyst shows very efficient retention of functional groups, as evident from its reusability up to 7 times. Thus the process is energy and cost efficient, with a potential for commercialization.

Facile synthesis of polypyrrole decorated chitosan-based magsorbent: Characterizations, performance, and applications in removing cationic and anionic dyes from aqueous medium

The adsorption characteristic of polypyrrole decorated chitosan-based magsorbent (MChs/Ppy) for the elimination of cationic crystal violet and anionic methyl orange dye from wastewater were explored. The characteristics of MChs/Ppy were studied by TGA, SEM/EDAX, TEM, BET, FTIR, VSM, and XRD analyses. The performance of MChs/Ppy towards the adsorption of CV and MO was investigated by the batch method. Removal performance was obtained to be 88.11 and 92.89% for CV and MO at the optimum conditions. The adsorption of CV was well described by pseudo 2nd order, while that of MO was best followed by the pseudo 1st order kinetics. The adsorption equilibrium data for both the dyes were fitted well with Langmuir adsorption isotherm with the maximum monolayer sorption capacity of 62.89 and 89.29 mg/g for CV and MO, respectively. The negative values of ΔH and ΔF accompanying with the removal of both dyes specified the adsorption process to be exothermic and spontaneous. Regeneration study showed that MChs/Ppy could be reused efficaciously up to three consecutive ad−/de-sorption cycles. The combined benefits of facile synthesis, non-toxicity, and good adsorption potential towards cationic and anionic dyes along with easy magnetic separability make MChs/Ppy as a novel adsorbent.

Vegetable residue of fenugreek (Trigonella Foenum-Graecum), waste biomass for removal of Basic Violet 14 from wastewater: Kinetic, equilibrium, and reusability studies

The present work has focused on the utilization of vegetable residue of Fenugreek (VRF), sustainable and novel adsorbent for sequestration of Basic Violet 14 (BV 14) dye. Effect of various batch operating parameters on BV 14 adsorption has been studied in detail and optimum values were reported as pH of 7.2, adsorbent loading of 0.125 g, shaking time of 105 min and temperature of 323 K. VRF was characterized based on various techniques as FTIR, DLS, zeta potential, SEM-EDS, and BET analysis. Kinetic and equilibrium data have been well exemplified by pseudo 1st order and Freundlich model, respectively. The maximum uptake capacity was reported to be significant as 177.78 mg/g. Mechanism of BV 14 adsorption on VRF was reported to involve steps as pore diffusion and film diffusion based on reported data fitting to Boyd model. Thermodynamic investigation affirmed adsorption as spontaneous, endothermic and physical in nature. Recovery of adsorbed BV 14 from VRF was conducted using ethanol as an elution media and regenerated VRF was applied for fresh BV 14 adsorption in five cycles. Recovery values were reported to be significant as 98.92% for first cycle and 84.41% for fifth cycle. Similarly, uptake capacity values were reported to be significant as 39.34 mg/g for first cycle and 32.47 mg/g for fifth cycle, which has proved the recovery potential and thus the applicability of VRF for subsequent cycles of BV 14 adsorption. Overall, the present work proved VRF as a promising adsorbent for successful remediation of BV 14 dye.

Extraction of cobalt ions from aqueous solution by microgels for in-situ fabrication of cobalt nanoparticles to degrade toxic dyes: A two fold-environmental application

Microgels were obtained by method of free radical precipitation polymerization and characterized by TEM, DLS and FTIR. Adsorption of Co2+ ions was studied under various conditions of pH, concentration of metal ions and that of microgels. Different adsorption isotherms were applied to study mechanism of adsorption process. Kinetics and mechanism of the adsorption process was investigated by pseudo 1st order, pseudo 2nd order and intra-particle diffusion modeling. In situ reduction of Co2+ ions loaded into the polymer microgel was carried out to get hybrid system for catalytic degradation of 4-nitrophenol, Eosin and Methylene blue.

Insights into endocrine-disrupting Bisphenol-A adsorption from pharmaceutical effluent by chitosan immobilized nanoscale zero-valent iron nanoparticles

Bisphenol A (BPA) in the aquatic environment have adverse effects on human health and other living organisms. BPA at low traces can lead to cardiovascular disease, type II diabetes, and impaired hepatic enzymes. For efficient BPA removal, chitosan immobilized nanoscale zero-valent iron (nZVI-chitosan) nanoparticles were synthesized and used as adsorbent. Since the BPA removal efficiency depends on independent process variables like nZVI-chitosan dosage, initial BPA concentration, pH and contact time, experiments were conducted systematically. To characterize the interaction effect of these variables, the experimental matrix is designed using response surface methodology (RSM). The isothermal and kinetic model parameters are estimated using differential evolution optimization (DEO), and these parameters better represent adsorption behaviour. The batch adsorption experiments indicated that the BPA adsorption on to nZVI-chitosan follows pseudo 1st order kinetic models. The maximum extent of BPA adsorption was 65.16 mg/g based on the Langmuir isotherm model. DEO based model parameters better fit the non-linear models with high R2 and lower RMSE. The regenerability experiments indicate that synthesized nZVI-chitosan adsorbent can be used up to three cycles with removal efficiency over 50%. The thermodynamic studies indicated that ΔG° is negative signifying a favourable and spontaneous adsorption process. The inhibition effects of coexisting ions on BPA adsorption followed the order of Mn2+ > Ca2+ > Mg2+ > Fe2+ for cations and of SO42− > NO3− > Cl− for anions. The BPA removal from real pharmaceutical wastewater is 93.8% obtained for optimal initial BPA concentration of 6 mg/L, an adsorbent dosage of 1.5 g/L, with solution pH of 3 and adsorption time of 1 h, whereas this removal efficiency is 95% for synthetic wastewater.