Order Kinetic Model Research Articles

Gamma Irradiation‐Assisted Synthesis of Nanocomposite Reinforced with Cellulose Nanocrystals Extracted from Sugarcane Bagasse to Adsorb Sr2+ Ions from Simulated Wastewater

AbstractSugarcane bagasse (SCB) can be investigated as an agro‐waste for various applications. Its suitability as a source of cellulose piqued interest across a variety of applications, especially in the industrial sector. The current study applied the acid hydrolysis method to successfully isolate cellulose nanocrystals (CNCs) from sugarcane bagasse for use as nano reinforcing agents. The formation of CNCs was confirmed by XRD, EDX, and DLS. The extracted CNCs were effectively generated by the ex‐situ method, dispersed into an Acacia gum/acrylamide (AG/AAm) solution, and subjected to γ‐irradiation for superpurity polymerization and crosslinking, generating AG/PAAm hydrogel and AG/PAAm/CNCs nanocomposite. The structure, morphology, and characteristics of AG/PAAm hydrogel and AG/PAAm/CNCs nanocomposite were evaluated using FTIR, SEM, TGA, and XRD. Hydrogel and the nanocomposite with improved characteristics as a result of CNCs reinforcement can be extremely beneficial in the elimination of simulated radioactive Sr2+ metal ions from wastewater. Batch adsorption examinations were executed to identify the optimum adsorption by modifying a variety of parameters including pH, adsorbent dosage (V/m ratio), initial pollutant concentration, temperature, and contact time. According to the results, the optimum pH enhancing the removal of Sr2+ ions was 9. The incorporation of CNCs into the AG/PAAm matrix enhances the adsorption of Sr2+ reaching 370 mg g−1. The results fit the pseudo‐second order kinetic model as well as the Freundlich isotherm.

Preparation and characterization of nano composites from metal oxides and activated carbon from banana peel (MO@BPAC, MO=NiO, CuO and ZnO) for 2 nitrophenol removal from aqueous solutions.

In this research, activated carbon from banana peel (BPAC) was prepared by calcination (600°C) method. Nano composites MO@BPAC (MO=NiO, CuO and ZnO) were prepared and then were characterized by XRD, FTIR, FESM, EDX, BETand TGA methods. Formation of MO@BPAC nanocomposites was confirmed by analysis methods. The XRD patterns showed formation of nanocomposites did not change crystalline phase of metal oxides. TGA analysis also showed the MO@BPAC had high thermal stability to 780°C. Removal of 2-nitrophenol by MO@BPAC nanocomposites was studied. The optimum contact time of 80min for NiO@BPAC, 100min and 120min for ZnO@BPAC and CuO@BPAC was observed. The order of percent removal of 2-nitrophenol by nanocomposites was as follow: NiO@BPAC>CuO@BPAC>ZnO@BPAC. The maximum removal of 2-nitrophenol 40mg L-1was attained at pH 9 and sorbent dose of 0.12g. The kinetic studies showed adsorption of 2-nitrophenol was described better by pseudo second order kinetic model than pseudo first order kinetic. The studies for equilibrium data showed Langmuir isotherm model gave better correlation with the experimental data (qe=303mgg-1 for NiO@BPAC). Thermodynamic parameters indicated adsorption of 2-nitrophenol by MO@BPAC nanocomosites were spontaneous and endothermic. The NiO@BPAC could be reused fourth cycles.

Fe2O3/polypyrrole/peanut husk composite for the adsorptive removal of Basic Blue 41 from the aqueous medium: Kinetics, equilibrium modeling and thermodynamic studies

In this study, Basic Blue 41 (BB41) was adsorbed from an aqueous medium using a peanut husk (PH) functional composite with polypyrrole/Fe3O4. For the adsorption of BB41 dye, the effects of process variables including pH, sorbent dose, dye concentration, agitation time, and temperature were investigated. The magnetic composite showed the highest efficiency for the adsorbents at pH 7-10, 0.05 g adsorbent dose, 90 min contact time and 200 mg/L initial dye concentration at 27 °C. The qe was found up to 48 mg/g with percentage removal of up to 96% for BB41 dye for the composite. On the experimental data of BB41 dye, the Langmuir, Freundlich, Temkin, Harkin-Jura, and Dubinin-Radushkevich isotherms were applied. The BB41 adsorption data were also subjected to pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models. Thermodynamic factors, such as the change in enthalpy (ΔH°), entropy (ΔS°), and Gibbs free energy (ΔG°), were also calculated. The results show that the BB41 adsorption process is exothermic and spontaneous. Techniques such as FT-IR and scanning electron microscopy (SEM) were used to characterize the composite materials. This study demonstrated the promising adsorption potential of magnetic/polypyrrole/peanut husk composites. This class of adsorbent could be used to remediate wastewater that contains dyes.

Freeze-drying synthesis of mesoporous magnetic grafted chitosan/calcium oxide nanoparticle for remazol brilliant blue dye removal: A statistical optimization

Herein, a mesoporous magnetic chitosan-salicylaldehyde/calcium oxide nanoparticle (CS-SL/CaO/Fe3O4) biocomposite adsorbent that was prepared via freeze-drying. The CS-SL/CaO/Fe3O4 was utilized for the adsorption of ramazol brilliant blue (RBB) dye from aqueous solution. The physicochemical properties of the CS-SL/CaO/Fe3O4 were evaluated using diverse characterization techniques, including BET, XRD, FTIR, FESEM-EDX, CHNS, and pHpzc. The three main factors for adsorption included the following A: CS-SL/CaO/Fe3O4 dosage (0.02–0.1 (g)/100 mL), B: pH (4–10), and C: Time (60–540 min). These factors were improved using statistical methods, specifically the Box-Behnken design (BBD). The optimal conditions for achieving maximum RBB removal (62.5 %) are listed: CS-SL/CaO/Fe3O4 dosage of 0.1 g/100 mL, a solution pH of 7, and a contact time of 540 min. The adsorption kinetics and equilibrium isotherms were well described by the pseudo first order (PFO) kinetic and Langmuir isotherm models, respectively. Thus, the CS-SL/CaO/Fe3O4 material has a maximum adsorption capacity (qmax) of 63.3 mg/g for RBB at 25 °C. The adsorption mechanism of RBB onto the CS-SL/CaO/Fe3O4 surface was attributed to electrostatic forces, n-π stacking, H-bonding, and Pi-Pi interactions. Thus, CS-SL/CaO/Fe3O4 represents a recoverable magnetic adsorbent with potential for capture of organic dyes from wastewater.

Experimental and ANN based process optimization for bioremediation of Cr6+ and Cd2+ by green adsorbent prepared from Artocarpus Heterophyllus leaves

The effective removal of toxic pollutants from water and waste water, is a challenging issue for environmental protection. In the present work, the performance of Artocarpus Heterophyllus (jackfruit) leaves have been examined for reduction of toxic Cr (VI) and Cd (II) from synthetic wastewater. Characterization of the adsorbent was made to evaluate the surface morphology and chemical composition, by Scanning Electron Micrograph (SEM) and Energy Dispersive Spectroscopy (EDS). Characteristic surface groups [Fourier Transform Infra-Red (FTIR)], surface area and surface structure [Brunauer–Emmett–Teller, (BET)] were also determined. The influences of various factors which control the removal process were studied experimentally in batch method and optimized. High removal efficiency was obtained at pH ≤ 2 for Cr (VI); and for Cd (II) it was ≥ 6. The experimental data were tested using different kinetic and isotherm models. Artocarpus Heterophyllus leaf was found suitable to remove 99.7 % Cr (VI) and 98.4 % Cd (II) from a strength of 20 mg L-1 solution at 0.5 g L-1 adsorbent concentration, at their respective favorable pHs. The reaction followed pseudo second order kinetic model for both the cases. The calculated sorption energy of 16.16 and 12.68 kJ mol-1, suggested chemical nature for both the cases. Desorption studies showed the effective reuse of Artocarpus Heterophyllus leaf for three times. The relatively high equilibrium adsorption capacity of 32.29 and 20.37 mg g-1 for Cr (VI) and Cd (II) respectively, suggested use of Artocarpus Heterophyllus leaf as a reasonably good green bio-adsorbent. The modeling of the complex adsorption process based on artificial neural network approach exhibited reliability and high degree of proficiency (R values of 0.999) in the model’s prediction and experimental data indicated its applicability in forecasting removal efficiency for both the metal ions.

High efficiency adsorption of boron by sodium alginate/polyethyleneimine/polysiloxane composite aerogel.

In this work, a new biomass boron adsorbent of N-methyl-D-glucosamine embedded sodium alginate/polyethyleneimine/polysiloxane composite aerogel (SKPN) was reported. Relevant characterization proved that the aerogel exhibited 3D porous structure with plenty of hydroxyl and amino functional groups, which was beneficial to the diffusion of boron and the chelation between boron and SKPN. Various parameters affecting the adsorption performance including pH value, contact time initial concentration, temperature and reusability were investigated. The maximum adsorption capacity was found at pH 8.0, and the adsorption capacity reached equilibrium within 3.75-5.75 h. Adsorption kinetics were more in line with the pseudo-second order kinetic model, suggesting the predominance of chemisorption. The adsorption isotherm was more in line with the Langmuir model, and the maximum adsorption capacities were calculated up to 38.41-49.39 mg/g (3.55-4.57 mmol/g) within the temperature range of 298 to 318 K, which were higher than most of the previous works. In addition, SKPN still showed good resistance to external ion interference and good reusability. The adsorption mechanism proved that the chelation interactions between boron and cis-diol and amino groups were the main driving forces. These results instructed that the adsorbent exhibited a good application prospect for boron adsorption, with the advantages of high adsorption performance, simple preparation process and environmental friendliness.

Kinetics of reduction of m‐iodonitrobenzene by aqueous ammonium sulfide under liquid–liquid phase transfer catalysis

AbstractHydrogen sulfide generated during hydrotreatment of sour crude oil fractions could be absorbed into aqueous ammonium hydroxide to produce ammonium sulfide. This ammonium sulfide can then be utilized to produce commercially valuable aromatic amino compounds by reducing the corresponding nitro compounds. In this work, the reduction of m‐iodonitrobenzene (m‐INB) to m‐iodoaniline (m‐IA) was performed by aqueous ammonium sulfide using a phase transfer catalyst, tetrabutylammonium bromide (TBAB). The study scrutinized the influences of various parameters such as concentrations of TBAB and m‐INB, as well as initial sulfide and ammonia concentrations, on the rate of reaction of m‐INB. An 11‐fold increase in reaction rate was obtained with only 0.09 kmol of catalyst TBAB per cubic meter of the organic phase. The selectivity of m‐IA was found to be100%. The reaction was found to be kinetically controlled with an activation energy of 40.0 kJ/mol. The rate of reaction of m‐INB was observed to be directly proportional to the concentrations of m‐INB, initial sulfide, and catalyst. A pseudo‐first order kinetic model was developed to correlate the conversion versus time data and an excellent agreement between observed and predicted reaction rates was obtained. The present work has very high commercial importance as it could be a viable alternative to the traditional Claus process to arrest H2S released by petroleum refineries.

Application of Carboxymethyl Cellulose (CMC)-Coated Nanoscale Zero-Valent Iron in Chromium-Containing Soil Remediation

Abstract: Nanofine zero−valent iron (nZVI) is a new, eco−friendly material with strong reducing and adsorbent properties that can be used to clean up heavy metal−affected soils. Herein, nZVI encapsulated with carboxymethyl cellulose (CMC−nZVI) is synthesized via an aqueous−phase reduction technique and subsequently deployed to evaluate its effectiveness in Cr(VI) soil remediation. The characterization analysis used SEM−EDS, XRD, XPS, and LSV to determine the relevant properties of the material. The results show that at an initial Cr(VI) concentration of 169.5 mg·kg−1, 93.2% of Cr(VI) was removed from the soil after 10 h of treatment with CMC−nZVI at pH 3.3. The kinetic analysis showed that CMC−nZVI had the maximum equilibrium adsorption capacity for removing Cr(VI) from soil at 105.3 mg·g−1. This followed a pseudo−second−order kinetic model. The study shows that CMC−nZVI converts Cr(VI) to Cr(III), which forms complexes with Fe(III) ions in the presence of hydroxide ions (OH−) to form a highly stable compound that eventually adsorbs into the nanomaterial’s surface for efficient removal.

Fe-modified Eriobotrya japonica seed biochar for removal of methylene blue: Isotherms, thermodynamic, kinetic studies

In this study, biochar and magnetic biochar were used to remove methylene blue from the aqueous solution. This study also presents the preparation of biochar and magnetic biochar. Biochar and magnetic biochar used as adsorbent substances were obtained from loquat seeds (Eriobotrya japonica). The prepared adsorbent materials were characterized using SEM-EDS, BET, XRD and FT-IR. The effects of pH, time, amount of biochar and magnetic biochar, initial methylene blue (MnB) concentration and temperature were investigated. The sorption of MnB on biochar of Eriobotrya japonica seeds (b-ER) and iron-modified (mb-ER) is an endothermic process. R2 values, calculated and experimental adsorption capacity values were compared (R2 = 0.992 b-ER-MnB and R2=0.983 mb-ER-MnB) b-ER and for mb-ER the MnB adsorption process was found to fit the pseudo-second order-kinetic model. It was found to be more suitable for Langmuir adsorption isotherms when the adsorption isotherms were investigated. The maximum adsorption capacity was 40.650 ± 2.036 mg/g for b-ER-MnB and 81.697 ± 4.085 mg/g for mb-ER-MnB. According to the results obtained, mb-ER can be used effectively in the removal of methylene blue from aqueous solutions.

Facile synthesis of amine functionalized silica coated iron oxide nanoparticles for highly efficient removal of cefixime and ceftriaxone from wastewater

ABSTRACT A novel adsorbent, amine-functionalized porous silica-coated iron oxide nanoparticles (Fe3O4@SiO2-NH2) was prepared for the removal of cefixime (CFX) and ceftriaxone (CFT) from water. The adsorbent was then characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy, transmission electron microscopy, particle size, surface area and pore size analysis. The particle size, surface area and pore size of amine functionalized silica coated iron oxide are 110 nm, 1073 m2/g and 40 Å, respectively. The effect of adsorbent dose, concentration, time duration, temperature and pH were evaluated. At optimum conditions, the removal efficiency of CFX and CFT was found to be 94.53% and 88.3%, respectively. The adsorption data of CFX and CFT onto Fe3O4@SiO2-NH2 were fully fitted with the Freundlich isotherm and followed pseudo-2nd order kinetic model. The adsorbent has strong interaction with CFX and CFT through hydrogen bonding. The adsorbent was regenerated and reused 30 times, and it was found that the removal efficiency of the adsorbent dropped only by 10%. Owing to high removal efficiency and easy preparation method, Fe3O4@SiO2-NH2 could be used as an efficient nano-adsorbent for the removal of antibiotics and other emerging contaminants from wastewater.

Evaluation of Cs+ and Sr2+ sorption behaviour of synthetic NaA and NaP zeolite modified with graphene oxide

NaP and NaA zeolites are the promising materials for removal of cesium (Cs+) and strontium (Sr2+) from nuclear waste, and the effective utilisation of these relies on the appropriate modification to enhance their ion exchange properties. In this aim, zeolite (NaZ) containing both NaA and NaP zeolites, and the composite of zeolite and graphene oxide (GO-NaZ), were synthesised by hydrothermal process and characterized by varieties of techniques, like XRD, Raman spectroscopy, scanning electron microscopy (SEM), gas adsorption, and small angle X-ray scattering (SAXS). Presence of both NaP and NaA phases was confirmed from XRD and Raman spectroscopy. SEM, SAXS and gas adsorption studies indicated presence of extensive macropores and rough surfaces in the samples. The sorption behaviours of the samples were studied using solutions of radioactive tracer or inactive ions, and the sorption efficiencies were evaluated by equilibrium and kinetic studies. Equilibrium studies indicated that the composites have higher Cs+ exchange capacity than the pristine NaZ. However, opposite trend was observed for Sr2+ ions. Kinetic studies revealed that the Sr2+ and Cs+ uptake follow pseudo-2nd order kinetic model. It was also revealed that GO-NaZ composite shows better selectivity for Cs+ over Na+ at lower concertation of Cs+, and hence it can be a promising material for site decontamination.

Cinética y microbiología de la fermentación durante el ensilaje de la pulpa de las hojas desfibradas de Agave salmiana

A new machine for decortication of residual leaves of Agave salmiana was developed, yielding, juice (43 ± 6 %), wet pulp (25 ± 3 %), and wet fiber (18 ± 4 %) with an overall 86 ± 2 % recovery. Production of lactic acid (LA) and acetic acid (AA) in micro silages of wet agave pulp were assessed together with the evolution of lactic acid bacteria (LAB) and mesophile bacteria (MB) populations. LA spontaneous fermentation was followed by a two stage first order kinetics model (R2 = 0.89), At the start (pH = 5) MB population was 100 times higher than LAB = 1xE8 CFU/g. Fermentation peak was reached at 11 days when pH = 4, LA = 119 g/kg, LAB = 4xE9 CFU/g, and MB = 1xE8 CFU/g showing that LAB overgrew MB. Average AA values were negligible during the first month. After two months, LA and AA titers were 80 and 40 g/kg, respectively. Pasteurized pulp with LAB < 1E2 CFU/kg showed, significant LAB growth after one week of silage (3xE7 CFU/g). Inoculation of pasteurized pulp by selected LAB strains produced lower counts (8xE9 CFU/g) as compared to spontaneous fermentations (9xE10 CFU/g). Hence, spontaneous agave pulp fermentation is a reliable process for conservation of agave pulp and seems worth scaling-up as the basis for ruminant production in the dry lands of Central Mexico. It remains to develop the utilization of the juice and fiber fractions of A. salmiana as the basis for new biochemical and textile industries.

Methylene blue and malachite green dyes adsorption onto russula delica/bentonite/tripolyphosphate.

In the current research Russula delica mushroom/bentonite clay (RDBNC) as a low-cost bionanosorbent was investigated for adsorption of methylene blue (MB) and malachite green (MG) dye from contaminated water. The bionanosorbent was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), Scanning electron microscopy (FESEM), Thermal Gravimetric Analysis (TGA), and Zeta-potential techniques. Adsorption experiments of RDBNC for MB, MG dyes following Freundlich isotherm and pseudo second order kinetic models. To determine their effects on the adsorption efficiency, the adsorption parameters were investigated including dye concentration, contact time, temperature, and dosage of the bionanosorbent. The adsorption process can operate through three primary mechanisms: the π-π interaction, the hydrogen bonding, and electrostatic interactions between the surface of RDBNC and MB, MG dyes. Desorption results revealed that MB and MG dyes were effectively desorbed during the fourth cycle without a notable loss in adsorption capacity. The thermodynamics parameters including ΔH, ΔS, and ΔG, were determined, and the adsorption process was favorable, spontaneous, and exothermic for MB and MG. The results showed that RDBNC, which showed effective inhibition at low concentrations, especially against E. coli, can be used as a low-cost bionanosorbent synthesised for the first time to remove industrial dyes.

Reduced graphene oxide – CeO2 nanocomposites for photocatalytic dye degradation

Over the past few decades, the widespread use of dyes has led to considerable environmental pollution, posing serious threats to human health and ecosystems. In this context, here focus on a tailored nanocomposite comprising reduced graphene oxide (rGO) and cerium oxide (CeO2) to eradicate methylene blue (MB) dye. The fabrication process involves a facile synthesis wherein CeO2 nanoparticles are anchored onto rGO sheets through co-precipitation treatment by mixing a precursor salt of cerium with graphene oxide (GO) in presence of reducing agent. The resulting nanocomposites were characterized using X-ray diffraction (XRD) analysis which confirms the crystallite size of CeO2 and rGO-CeO2 determined to be 21.61 nm and 10.74 nm respectively. Further FE-SEM analysis vividly illustrates the relatively spherical form of CeO2, which is dispersed on the rGO surface and energy dispersive X-ray spectroscopy (EDX) results provide clear evidence of the presence of carbon, cerium and oxygen in the composite. Additionally, Fourier-transform infrared spectroscopy (FTIR) confirms the composition of the rGO-CeO2 nanocomposites demonstrating the existence of various oxygen-containing groups, including O–H, C=O and Ce–O bonds. Thermogravimetric analysis (TGA) highlights that the rGO-CeO2 nanocomposites exhibits higher thermal stability with only 21.88 % weight loss up to 400 °C. Moreover, the photocatalytic activity of rGO-CeO2 nanocomposite exhibits a remarkable 94.92 % degradation of MB dye within 80 min under optimal conditions of UV light irradiation (λ = 254 nm), with a catalyst dosage of 7 mg in a 20 ppm of MB dye solution at pH 9. In contrast, pristine rGO and CeO2 achieved only 32.27 % and 38.48 % in 100 and 90 min respectively. The kinetics of photocatalysis process were meticulously studied and revealed that they followed pseudo-second order kinetic model suggesting chemisorption of MB dye onto nanocomposites prior to degradation. The stability of the nanocomposite was assessed under optimal conditions, demonstrating robust MB degradation (78 %) even up to the 4th cycle. Overall, the successful outcomes of this study show significant potential for degrading MB dye in wastewater by using the rGO-CeO2 nanocomposite.

Graphene oxide and hydroxyapatite-based composite extracted from fish scale: Synthesis, characterization and water treatment application

In this study the removal of hydrocarbon pollutants from refinery waste water has been described through a convenient adsorption technique using a novel composite of graphene oxide (GO) and n-hydroxyapatite (n-HAp). The main aim was to synthesized composite which are not only sustainable and biodegradable but also exhibit high adsorption capacity and selectivity for hydrocarbon pollutants. Both the HAp and GO were synthesized from fish scales in the laboratory. The synthesized material was then characterized by XRD, FTIR, SEM, and EDX. At 40 °C and 80 min of reaction time, the adsorbent utilized in a batch mode study attained a maximum 97 % organic pollutant adsorption rate. The adsorption activity was spontaneous, exothermic, useful, and it adhered to the pseudo-2nd order kinetic model. without noticeably losing its activity, the adsorbent retained a high level of efficiency over four consecutive cycles. Adsorption of hydrocarbon wastes using composite adsorbent was carried out under batch mode of adsorption experiments. We also studied the effect of dose, temperature, time and pH of the solution on adsorption. Ethanol was used to regenerate the adsorbent, and it was then dried at 70 °C for re-use. The SEM investigation showed that the morphology of huge caves is rough, layered, and wrinkled. The oxygen and phosphate containing groups were found via FT-IR analysis. Freundlich and Langmuir kinetic models were used to measure the adsorption behavior by applying them to the adsorption data. The results demonstrated a strong correlation between the Freundlich isotherm model and the real data. This study showed a highly effective and cost-efficient methodology for the removal of toxic hydrocarbon contaminants in refinery wastewater.

Investigation of the adsorptive capacity of a poly(vinyl alcohol)-based film for sodium diclofenac in aqueous media

Sodium diclofenac (DCF) has been detected in waters worldwide and is considered a micropollutant of emerging concern due to its potential toxicity in aquatic and terrestrial ecosystems. Traditional water treatment methods are unable to remove DCF completely from water, which makes adsorptive films a suitable alternative to address this challenge. In this context, the present study investigated the adsorptive capacities of a poly(vinyl alcohol)-based film for removing DCF from aqueous solutions. The effects of the initial DCF concentration and solution pH on the adsorption performance were evaluated, as well as kinetics and equilibrium isotherms. Regarding the results, DCF precipitation was observed within a pH range of 4.0-7.0, probably due to its limited solubility in acidic media. The optimal DCF concentration was found to be the lowest tested (2.5 mg L-1), yielding an equilibrium adsorption capacity (qe) of 0.511 mg g-1 and a DCF removal percentage (%R) of 23.4% within 90 min. Although the adsorption equilibrium was well described by the Redlich-Peterson isotherm despite the unusual behavior observed, pseudo-first and pseudo-second order kinetic models were satisfactory only at the initial concentration of 2.5 mg L⁻¹. Overall, the data set indicate that the film has a limited adsorption capacity, reaching saturation at low adsorbate concentrations. Nonetheless, these findings support further investigations at lower DCF concentrations to better understand the film’s adsorptive behavior under environmentally relevant conditions.

Engineered Mg-modified biochar-based sorbent for arsenic separation and pre-concentration

The utilization of biochar as a relatively efficient sorbent or stationary phase for the separation and preconcentration of a wide range of analytes represents an innovative approach in current sample pretreatment methods. Appropriate pre- and post-pyrolysis modification of the input precursor and pyrolysis product, respectively, allows targeted design of the physicochemical properties and sorption characteristics of the resulting sorbent. The present work deals with the preparation of pyrolysis materials based on unmodified cattail leaf biomass (BC) and its Mg-modified analogue (MgBC) by a slow pyrolysis process at 500 °C and a residence time of 1 h in a pyrolysis reactor. Physicochemical characterization of BC and MgBC carried out by pH, total C, N, surface size analysis (SSA), 13C NMR, SEM-EDX and XRD confirmed significant morphological and mineralogical differences between the prepared sorbents. By performing sorption experiments using a model anionic analyte (As) and application of Langmuir isotherm, we found that the predicted maximum sorption capacity of MgBC for As is 13.5-fold higher than that of BC. The sorption process of As by both sorbents is best described by the Sips adsorption isotherm (R2 ≥ 0.995) and a pseudo-nth order kinetic model (R2 ≥ 0.997). The optimum pH for As sorption by BC and MgBC sorbents is in the interval 5–6. The presence of competitive phosphate anions (equimolar concentration of 1:1) in the solution significantly reduces the sorption capacity of MgBC for As by 40% for BC by 70%. The presence of Cl- ions showed no significant effect on the sorption capacity of Bc and MgBC for As. Both sorbents were best recovered using 0.1 mol/L NaOH solution when the desorption efficiency for both sorbents was more than 95%. The MgBC sorbent showed 35% retention of As from the real sample in the model SPE column at a flow rate of 0.12 mL/s. Based on the obtained knowledge, it is evident that biochar-based sorbent prepared from Mg-modified precursor represents an effective sorbent for anionic forms of analytes and opens the possibility of its use also in preconcentration and separation techniques.

Multifunctional Copper Sulfide Urchin‐Like Nanostructures for Adsorption and Photocatalysis of Water Contaminants

AbstractWe reported here a one‐step chemical route to prepare nanocomposites comprising CuS nanophases supported on GO sheets with magnetic properties. The synthesis reported here combines such materials in single‐nanostructures that show morphological features well‐suited for wastewater treatment. The photocatalytic performance of CuS/GO nanocomposites was first investigated towards the removal of a common organic dye (rhodamine B) and sulfamethoxazole (SMX), which is an antibiotic considered a water contaminant of emerging concern. The RhB and SMX adsorption efficiency of CuS/GO and Fe3O4/GO/CuS hybrids, as well as of CuS particles, was significantly higher than GO or Fe3O4/GO. Overall, the CuS‐based magnetic and CuS/GO hybrids have shown the capacity to uptake more than 80 % of RhB or SMX, after 120 minutes. Under blue‐led irradiation, almost complete degradation of RhB was achieved in the presence of CuS/Fe3O4/GO, after 180 minutes; and higher than 85 % degradation of SMX, after 240 minutes of irradiation. The photocatalytic behaviour of nanocomposites was best described by the first–order kinetic model, for which k values for degradation of RhB and SMX followed the order: CuS/Fe3O4/GO>CuS/GO>CuS. The tricomponent CuS/Fe3O4/GO can be easily recovered after use and be reused maintain their high photocatalytic performance, thus providing a sustainable and cost‐effective hybrid solution for water treatment.

Fabrication of tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel and its application as an adsorbent for copper ion removal

An effective tannic acid-incorporated polyvinylpyrrolidone/polyvinyl alcohol composite hydrogel with high-potential sorption capacity was developed for the removal of copper from aqueous solution. The composite hydrogel exhibited pH-dependent swelling, in which swelling and shrinking occurred reversibly with adjustment of the pH of the medium. At pH 4, the maximal adsorption capacity for copper at 30 °C was 297.0 mg g-1, and the adsorbent dose was 4 g L-1. The adsorption kinetics were best fitted with a pseudo-second order kinetic model. The adsorption behavior was well predicted by the Freundlish isotherm. The thermodynamics parameters indicated a spontaneous and exothermic reaction with an increase in the entropy of the system. The chemical changes in the film structure before and after adsorption treatment were characterized by Scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). The FTIR, XPS and XAS results confirmed that Cu bound to the oxygens in the -OH, C = O and N-(C = O)- functional groups on the T-HD. XAS analysis revealed the chemical composition and molecular geometry of the adsorbed copper ions. The single-solute adsorption and coadsorption mechanisms, which provide insight into cobalt-copper, nickel-copper, or nickel-cobalt-copper complex solutions, were investigated. The composite hydrogel exhibited excellent regeneration ability in EDTA solution. Notably, the adsorbent retained an adsorption efficiency exceeding 87% even after five regeneration cycles. On the basis of both adsorbent characteristics and adsorption performance, it was determined that the composite hydrogel has the potential to be used as a platform for developing materials to treat wastewater containing high levels of metal contaminants such as those from the electroplating industry.

In Situ Potentiometric Monitoring of Nitrate Removal from Aqueous Solution by Activated Carbon and Ion Exchange Resin.

A nitrate selective electrode was used for real-time in situ potentiometric monitoring of a batch nitrate removal process using activated carbon and ion exchange resin. A plasticized polymeric membrane consisting of polyvinyl chloride, 2-nitrophenyl octyl ether and tridodecyl methyl ammonium chloride was incorporated into an ion-selective electrode body. First, the dynamic potential response of the electrode to nitrate was investigated. Two commercial activated carbons with different physical properties were then tested. Nitrate removal with these carbons was monitored potentiometrically using several nitrate concentrations. The extreme turbidity of the solutions was not a drawback during potentiometric monitoring of the process, which is a clear advantage over other methods such as optical monitoring. The potential versus time recordings were converted into nitrate concentration versus time plots, which were evaluated with different adsorption kinetic models. A pseudo-second order kinetic model for nitrate adsorption on both activated carbons was found to fit the experimental data very well. The values of the kinetic parameters were very different between the two activated carbons. The proposed methodology was also satisfactorily applied to the study of nitrate removal by an ion exchange resin. In this case, the experimental results clearly follow a pseudo-first order kinetic model. Potential applications of the proposed methodology for monitoring nitrate removal in real water samples are discussed.