Redlich-Peterson Models Research Articles

Fabrication of versatile Ag-P/Ppy core-shell nanocomposite: Adsorption efficacy for chromium (VI) removal and assessment of antioxidant and antibacterial activities

This study reports the synthesis, via in-situ chemical oxidative polymerisation, of conducting polymer-based silver phosphate Polypyrrole (Ag-P/Ppy) core-shell nanocomposite, exhibiting antioxidant and antibacterial characteristics, for the adsorption of chromium (VI) ions from aqueous solutions. Filtering away Cr (VI) ions efficiently also improves the filtered water with antibacterial and antioxidant properties. P-XRD, ATR-FTIR, FESEM, EDAX, TEM, zeta potential, TGA, and BET studies characterized Ag-P/Ppy. The core-shell nanostructure of Ag-P/Ppy was determined by TEM micrographs, which indicated the presence of an Ag-P core and a Ppy shell. pH value, adsorbent dose, stirring rate, contact time, and Cr (VI) pollutant concentration, were investigated as potential influencing factors. At pH 2, 99.4 % of Cr(VI) was removed in 55 min. The adsorption kinetics was effectively depicted by a pseudo-second-order kinetics model, signifying that chemisorption played a momentous role in the total adsorption capacity. Freundlich, Temkin, Redlich-Peterson, and Sips isotherm models were fitted to adsorption data. Temkin and Redlich-Peterson models have a higher (0.99) correlation coefficient than Freundlich (0.95) and Sips (0.98). The maximum adsorption capacity (qm) evaluated using the Sips model was 138.5 mg g−1, which was quite close to the 130.55 mg g−1 value obtained from experiments. The manufactured nanocomposite showed 91.2 % radical scavenging activity in a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Antibacterial activity of the Ag-p/Ppy core-shell nanocomposite contrary to gram-positive (S. aureus) and gram-negative (P. aeruginosa, E. coli, and K. pneumoniae) bacteria was assessed by means of the agar well diffusion technique. Compared to the positive control, it inhibited S. aureus, E. coli, K. Pneumoniae, and P. Aeruginosa by 82.35 %, 79.5 %, 63.63 %, and 76.7 % respectively. Therefore, the Ag-P/Ppy core-shell nanocomposite has the potential as a potent and versatile adsorbent for the exclusion of Cr (VI) ions from water.

Sequestration of diclofenac and amoxycillin pharmaceutical compounds by thiourea modified poly(acrylonitrile-co-acrylic acid): parametric optimisation, kinetic and isotherm studies

ABSTRACT It has been previously reported that thiourea modified poly(acrylonitrile-co-acrylic acid) (TMPAA) could successfully be employed as polymeric adsorbent for the sequestration of cationic dyes and nitro-phenol. In this research, parametric optimisation, kinetic and isotherm analyses on the sequestration of diclofenac (DCF) and amoxycillin (AMX)) by TMPAA were investigated for the first time. The central composite design (CCD) results revealed that the optimisation exhibited high significance and reliability. The analysis of variance (ANOVA) indicated that TMPAA dose, antibiotic concentration and adsorption time exhibited high significance effect on the DCF and AMX sequestration. The 3D response surface plots showed notable antagonistic interaction among the adsorption parameters. A maximum DCF uptake of 97.94% was achieved under optimum condition of 0.1 g TMPAA dose, 25 mg/L, and 54 min, while 94.06% AMX removal was obtained at 0.1 g sorbent dosage, 25 mg/L, and 34 min contact time. Predicted and experimental results confirmed the accuracy of the established optimal conditions for both antibiotics. It was discovered by adsorption analysis that the pseudo-second-order kinetic and Redlich-Peterson models agreed with the adsorption kinetic and isotherm data. The findings suggest that the synthesised TMPAA polymer is capable of removing DCF and AMX from aqueous solutions.

Binary adsorption isotherms of methylene blue and crystal violet on mandarin peels: prediction via detailed multivariate calibration and density functional theory (DFT) calculations.

The multicomponent adsorption of synthetic dyes has great relevance in the treatment of effluents due to the complexity of the adsorbate-adsorbent interactions. Therefore, this study provides useful information about the adsorption capacity of methylene blue (MB) and crystal violet (CV) in a bioadsorbent (mandarin peels) in a single-component and competitive system using detailed multivariate calibration analysis. The PLS1 multivariate calibration model was used to quantify the adsorbates. In mono and two-component systems, the adsorption capacity of CV (1.26-1.36 mg g-1) was superior when compared to MB (0.925-0.913 mg g-1), characterizing synergistic adsorption for CV and antagonistic adsorption for MB. The Sips model was effective for describing single-component systems, suggesting that adsorption did not occur in the monolayer. For competitive adsorption, modified, unmodified, and extended models were used to understand the interactions between the dyes and the bioadsorbent. The modified Redlich-Peterson (MRP) model was effective in describing the behavior of the binary system, indicating that the interaction forces with the adsorbate were significant. Thus, the bioadsorbent showed promising results for competitive adsorption, thus being of relevance to the industrial sector. Density functional calculations were also performed to characterize the atomic interactions for the removal of both dyes on mandarin peels.

Synthesis, Characterization, and Adsorption Properties of Nitrogen-Doped Nanoporous Biochar: Efficient Removal of Reactive Orange 16 Dye and Colorful Effluents.

In this work, nitrogen-doped porous biochars were synthesized from spruce bark waste using a facile single-step synthesis process, with H3PO4 as the chemical activator. The effect of nitrogen doping on the carbon material's physicochemical properties and adsorption ability to adsorb the Reactive Orange 16 dye and treat synthetic effluents containing dyes were evaluated. N doping did not cause an important impact on the specific surface area values, but it did cause an increase in the microporosity (from 19% to 54% of micropores). The effect of the pH showed that the RO-16 reached its highest removal level in acidic conditions. The kinetic and equilibrium data were best fitted by the Elovich and Redlich-Peterson models, respectively. The adsorption capacities of the non-doped and doped carbon materials were 100.6 and 173.9 mg g-1, respectively. Since the biochars are highly porous, pore filling was the main adsorption mechanism, but other mechanisms such as electrostatic, hydrogen bond, Lewis acid-base, and π-π between mechanisms were also involved in the removal of RO-16 using SB-N-Biochar. The adsorbent biochar materials were used to treat synthetic wastewater containing dyes and other compounds and removal efficiencies of up to 66% were obtained. The regeneration tests have demonstrated that the nitrogen-doped biochar could be recycled and reused easily, maintaining very good adsorption performance even after five cycles. This work has demonstrated that N-doped biochar is easy to prepare and can be employed as an efficient adsorbent for dye removal, helping to open up new solutions for developing sustainable and effective adsorption processes to tackle water contamination.

Cellulose nanofibers decorated with SiO2 nanoparticles: Green adsorbents for removal of cationic and anionic dyes; kinetics, isotherms, and thermodynamic studies

Cellulose nanofibers decorated with SiO2 nanoparticles (SiO2-CNF) were prepared by the extraction of cellulose nanofibers from Yucca leaves, followed by modification with SiO2 nanoparticles, and used as efficient materials for the removal of both anionic and cationic dyes from the aqueous solution. Prepared nanostructures were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction powder (XRD), Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM) analysis. The adsorption capacity of the nanostructures was investigated for the removal of both cationic (Methylene Blue, MB, and Crystal Violet, CV) and anionic (Eriochrome Black-T, EB) dyes. The kinetics of adsorption were investigated using some well-known models, including intraparticular diffusion (IPD), pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich. The adsorption isotherms were also explored using the Langmuir, Freundlich, Temkin, and Redlich-Peterson models. The obtained results revealed that the adsorption processes follow PSO kinetic and Langmuir isotherm models. Thermodynamic parameters of the adsorption were measured at different temperatures, indicating the feasibility and spontaneity of the adsorption. The pH and salt effects on adsorption were also explored. Finally, according to the reusability tests, the prepared adsorbents showed high recoverability without considerable loss in adsorption efficiency after five repeated runs.

Synthesis of a chitosan@hydroxyapatite composite hybrid using a new approach for high-performance removal of crystal violet dye in aqueous solution, equilibrium isotherms and process optimization

BackgroundNovel chitosan and hydroxyapatite-based bio composites were studied as potential adsorbents for the removal of crystal violet, a cationic dye, present in an aqueous solution employing various experimental metrics such as initial concentration, pH, adsorbent mass, contact time, temperature, and effect of agitation. MethodsThe biosorbent was analyzed by several techniques such as Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), specific surface by BET theory, thermal analysis ATG and X-ray energy dispersal (EDS). Significant FindingsThe present study focuses on the synthesis of chitosan, a polymer extracted from shrimp shells, and its association with synthesized hydroxyapatite to form a Cs@Hap composite effective for the adsorption of a cationic dye, crystal violet. The physical and functional properties of the composite were studied using several techniques. X-ray diffraction confirmed the formation of the composite by its crystalline structure, infrared analysis revealed the presence of NH, OH and PO functional groups responsible for the adsorption, SEM coupled with EDS as well as BET and ATG allowed to characterize the surface of the composite as porous, rough and heterogeneous, with an SSA of 138.47 m2g−1, perfect for the adsorption of the given dye. The resulting adsorption efficiency is high and was able to reach a maximum of 93.21% through the optimization of the parameters affecting the adsorption, namely an adsorbent mass of 0.1 g at a pH value equal to 6.5. The kinetic, isothermal and thermodynamic study showed that the adsorption was endothermic and follows the pseudo-second order and Redlich-Peterson models. The regression coefficient R²= 0.9219 showed the validity of the response surface methodology coupled to the Box Behnken design (RSM-BBD) in predicting the percent removal of CV by adsorption.

Bioaugmentation of Cd(II) removal in high-salinity wastewater by engineered Escherichia coli harbouring EC20 and irrE genes

Wild strain generally can remove heavy metals but cannot tolerate high-salinity. In this study, Cd(II) adsorption protein EC20 on the cell surface and global regulator irrE in the cytoplasm of Escherichia coli were expressed to adsorb Cd(II) in high-salinity conditions. The maximum adsorption amount was 30.79 mg/g at 30.84 mg/L Cd(II) and 2% NaCl of E. coli (EC20/irrE), which was higher than E. coli (p23), E. coli (EC20) and E. coli (irrE). The adsorption kinetics fitted well with the Elovich model. And Redlich-Peterson model was used to describe the adsorption process successfully. Transcriptome data analysis showed that the overexpression of irrE in E. coli significantly increased high-salinity tolerance, because of trehalose accumulation and exopolysaccharide export. Subsequently, a bioaugmentation sequencing batch reactor was adopted for treating the actual Cd(II) contained high-salinity petrochemical wastewater. The results showed that the chemical oxygen demand and Cd(II) removal reached up to 96.17% and 97.60%, higher than the control group of 79.15% and 92.09%, under the influent chemical oxygen demand of 1715 mg/L, Cd(II) of 4.63 mg/L and salinity of 3.0% in bioaugmented system. 16S rRNA analysis revealed that the microbial community in the bioaugmented system adapted to the high-salinity and Cd(II) stress which proved the superiority of bioaugmentation. Finally, a mechanism for high-salinity tolerance in sequencing batch reactor was revealed and provides a basic foundation for the engineered strain to treat Cd(II) containing high-salinity wastewater. This study will promote the understanding of the effect of engineered strains bioaugmentation on the treatment of heavy metals and other pollutants in high-salinity wastewater.

Combination with litchi procyanidins under PEF treatment alters the physicochemical and processing properties of inulin.

A novel alternative to prepare the inulin-procyanidin complex assisted by pulsed electric field (PEF) treatment was explored in this study. Results showed that the optimal condition of PEF treatment enhanced the adsorption rate of procyanidins to inulin from 78.56 to 103.46μg/mg. Based on well fitted by Redlich-Peterson model and spectral analysis including UV and FT-IR, the interaction between inulin and procyanidin was evidenced to be dominated by hydrogen bonds. The DSC curve and the SEM spectrum displayed better stability of the PEF-treated inulin-procyanidin complex than the untreated complex. The PEF-treated complex had lower solubility but higher water-holding capacity than inulin, which exhibited stronger shear-thinning property and more stable flow behavior referring to rheological analysis. Furthermore, the gel formed from the PEF-treated complex possessed greater hardness, chewiness and viscosity, with no significant effects noted in terms of springiness, cohesiveness and resilience.

Bamboo sawdust-derived high surface area activated carbon for remarkable removal of paracetamol from aqueous solution: sorption kinetics, isotherm, thermodynamics, and regeneration studies

Abstract Due to its widespread consumption, paracetamol (PCT) has emerged as one of the leading contaminants that pollute water. Herein, a PCT removal of 99.6% was achieved using chemically activated carbon (CAC), derived from bamboo sawdust using KOH/FeCl3 as an activating agent, at optimal conditions of PCT (20 mg/L), CAC (0.5 g/L), contact time (90 min), and pH (8). Kinetic study revealed that the PCT adsorption process followed the pseudo-second-order kinetic model (R2 = 0.99), indicating that chemical adsorption dominated the adsorption mechanism. On the other hand, isotherm experimental data were best described by the Langmuir (R2 = 0.98) and Freundlich (R2 = 0.96) models. CAC had a maximum Langmuir monolayer capacity of 188.67 mg/g at a PCT concentration of 120 mg/L. Moreover, the Redlich–Peterson model gave the best fit (R2 = 0.99) to the experimental data, confirming that PCT adsorption was monolayer adsorption onto the heterogeneous surface. Thermodynamically, the PCT adsorption was exothermic, spontaneous, and favorable. The reusability study depicted that CAC can be successfully reused for five consecutive adsorption–desorption cycles. Furthermore, the application of CAC to environmental samples showed interesting results. The overall adsorption study indicated that CAC could serve as a promising adsorbent for eliminating PCT from water.

Iron-Iron Oxide Core-Shell Nanochains as High-Performance Adsorbents of Crystal Violet and Congo Red Dyes from Aqueous Solutions.

The main aim of this work was to use the iron-iron oxide nanochains (Fe NCs) as adsorbents of the carcinogenic cationic crystal violet (CV) and anionic Congo red (CR) dyes from water. The investigated adsorbent was prepared by a magnetic-field-induced reduction reaction, and it revealed a typical core-shell structure. It was composed of an iron core covered by a thin Fe3O4 shell (<4 nm). The adsorption measurements conducted with UV-vis spectroscopy revealed that 15 mg of Fe NCs constituted an efficient dose to be used in the CV and CR treatment. The highest effectiveness of CV and CR removal was found for a contact time of 90 min at pH 7 and 150 min at pH 8, respectively. Kinetic studies indicated that the adsorption followed the pseudo-first-order kinetic model. The adsorption process followed the Temkin model for both dyes taking into account the highest value of the R2 coefficient, whereas in the case of CR, the Redlich-Peterson model could be also considered. The maximal adsorption capacity estimated from the Langmuir isotherms for the CV and CR was 778.47 and 348.46 mg g-1, respectively. Based on the Freundlich model, both dyes adsorbed on the Fe NCs through chemisorption, but Coulombic interactions between the dye and adsorbent cannot be excluded in the case of the CV dye. The obtained results proved that the investigated Fe NCs had an excellent adsorption ability for both dye molecules within five cycles of adsorption/desorption, and therefore, they can be considered as a promising material for water purification and environmental applications.

Multimetal removal in aqueous medium using a potato starch/nopal mucilage copolymer: A study of adsorption kinetics and isotherms

In reducing heavy metals from water for direct or indirect consumption, various synthetic materials have been used; there is a tendency to use natural, biodegradable, and environmentally friendly materials. The aim was to elaborate copolymers with native potato starch and cactus mucilage and evaluate water's multimetal removal capacity. The copolymer was characterized, and the kinetics and adsorption isotherms were evaluated. The copolymers presented high solubility for nopal mucilage levels of 5% w/w, with particle size in aqueous solution less than 422.83 nm, zero charge point around pH 5.5, and potential ζ between −16.72 and −29.80 mV; FTIR analysis showed the predominance of anionic groups with chelating capacity. Multimetal adsorption was from 102.20 to 151.43 mg/g, with affinity in the order Pb > As > Al > Hg > Cr, being higher at pH 6 (p-value<0.05). Kinetic data were fitted to the PSFO, PSSO, and Elovich models with R2>0.994, X2<16.098, ARE<34.038, and random residual dispersion, indicating a chemisorption process. The adsorption isotherms were adjusted to the Langmuir, Freundlich, and Redlich-Peterson models with R2>0.863, whose parameters are related to the ionic radius of the metals, with favorable adsorption and a heterogeneous surface of the copolymer. The mean adsorption energy was found between 0.05 and 0.23 kJ/mol. The use of native potato starch and cactus mucilage allows the formulation of copolymers with high multimetal adsorption potential in aqueous systems.

Research on the performance of modified blue coke in adsorbing hexavalent chromium

To solve the issue of hexavalent chromium (Cr(VI)) contamination in water bodies, blue coke powder (LC) was chemically changed using potassium hydroxide to create the modified material (GLC), which was then used to treat a Cr(VI)-containing wastewater solution. The differences between the modified and unmodified blue coke’s adsorption characteristics for Cr(VI) were studied, and the impact of pH, starting solution concentration, and adsorption period on the GLC's adsorption performance was investigated. The adsorption behavior of the GLC was analyzed using isothermal adsorption models, kinetic models, and adsorption thermodynamic analysis. The mechanism of Cr(VI) adsorption by the GLC was investigated using characterization techniques such as Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscope (FE-SEM), X-Ray Diffraction (XRD), and X-Ray Photoelectron Spectroscopy (XPS). With the biggest difference in removal rate at pH = 2, which was 2.42 times that of LC, batch adsorption experiments revealed that, under the same adsorption conditions, the GLC always performed better than LC. With a specific surface area that was three times that of LC and an average pore diameter that was 0.67 times that of LC, GLC had a more porous structure than LC. The alteration significantly increased the number of hydroxyls on the surface of GLC by altering the structural makeup of LC. The ideal pH for removing Cr(VI) was 2, and the ideal GLC adsorbent dosage was 2.0 g/L. Pseudo-second-order kinetic (PSO) model and Redlich-Peterson (RP) model can effectively describe the adsorption behavior of GLC for Cr(VI). Physical and chemical adsorption work together to remove Cr(VI) by GLC in a spontaneous, exothermic, and entropy-increasing process, with oxidation–reduction processes playing a key role. GLC is a potent adsorbent that can be used to remove Cr(VI) from aqueous solutions.

The Effect of Sorbent Composition on Sorption Properties of Materials Based on Ti-Ca-Mg Phosphates.

Individual titanium and calcium-magnesium phosphates are widely known as effective sorbents. The sorption processes on these phosphates are based on different mechanisms. The sorption efficiency towards different cations depends on the phase composition of the sorbent. Composite materials with various ratio Ti:(Ca+Mg) have been synthesized. The sorption properties of samples obtained towards Cs+, Sr2+, Co2+, Cd2+, Zn2+, Cu2+, and Pb2+ have been studied to establish the effect of sorbent composition on metal removal. The adsorption isotherms have been analyzed using the Langmuir, Freundlich, and Redlich-Peterson models. The composition of sorbents has no effect on the level of removal of readily hydrolyzable Pb2+ and Cu2+ cations. Removal of lead occurs preferentially via the precipitation of metal phosphates and hydroxides. Copper precipitates as hydroxide in case of a high share of Ca-Mg phosphates in the composite sorbent. The removal of cesium proceeds according to the ion exchange mechanism only. For Cd2+, Co2+, Sr2+, and Zn2+ cations, the sorption efficiency on the composite materials synthesized is found to increase with the increase in titanium phosphate's share in the sample. All composite sorbents synthesized demonstrated a considerable increase in the level of purification of solutions studied compared with individual Ti and Ca-Mg phosphates due to the synergism of the components.

New Hybrid Adsorbents Based on Polyaniline and Polypyrrole with Silicon Dioxide: Synthesis, Characterization, Kinetics, Equilibrium, and Thermodynamic Studies for the Removal of 2,4-Dichlorophenol.

In the current study, polyaniline and polypyrrole with silicon dioxide (PAni:PPy@SiO2) were combined to formulate a new adsorbent, which was examined using XRD, TEM, SEM, FTIR, TGA, and BET, and the adsorption kinetics were investigated by UV-vis spectroscopy. The optical band gap was also evaluated. The electrochemical behavior was investigated using cyclic voltammograms. Moreover, experimental conditions were used to evaluate the 2,4-dichlorophenol (2,4-DCP) adsorption based on the pH, temperature, reaction time, and initial concentration. The analytical isotherm data were determined by Langmuir, Freundlich, Temkin, Sips, and Redlich-Peterson models. For the analysis of the kinetic data, the pseudo-first- and -second-order models and the intraparticle diffusion model were investigated. It was found that this new adsorbent possessed the highest adsorption efficiency after several regeneration cycles. Furthermore, the thermodynamic parameters of adsorption, such as entropy (ΔS), enthalpy (ΔH), and standard Gibbs were measured. These results suggest that the PAni:PPy backbone can generally be better applied for the elimination of 2,4-dichlorophenol by appropriately dispersing it over the surface of suitable SiO2. This search provides a novel way to develop separable, high-performance adsorbents for adsorbing organic contamination from wastewater.

Adsorption of Hg(II) on polyethyleneimine-functionalized carboxymethylcellulose beads: Characterization, toxicity tests, and adsorption experiments

Mercury (Hg) is widely used in many industrial processes and is released into the environment. Therefore, efficient removal of Hg from water is of vital importance worldwide. Here, we explored the adsorption characteristics of Hg(II) on polyethyleneimine-functionalized carboxymethylcellulose (PEI-CMC) beads and studied the toxicity of the beads toward Daphnia magna and Pseudokirchneriella subcapitata. The PEI-CMC beads had an average particle size of 2.04 ± 0.25 mm, a point of zero charge (pHpzc) of 5.8, and a swelling ratio of 2.45. Acute toxicity tests demonstrated that the PEI-CMC beads had no toxic effects on D. magna. The growth inhibition tests revealed that growth inhibition of P. subcapitata could be attributed to adsorption of trace elements in growth media on the PEI-CMC beads. The adsorption experiments exhibited that the Matthews and Weber model best described the kinetic data, whereas the Redlich–Peterson model was well fitted to the isotherm data. The theoretical maximum Hg(II) adsorption capacity of the PEI-CMC beads was 313.1 mg/g. The thermodynamic experiments showed endothermic nature of the Hg(II) adsorption on the PEI-CMC beads at 10–40 °C. The adsorption experiments exhibited that the Hg(II) adsorption capacity decreased gradually as pH increased from 2 to 12. The adsorption of Hg(II) on the PEI-CMC beads can occur through chelation and electrostatic attraction. The FTIR and XPS spectra before and after Hg(II) adsorption confirmed that chelation of neutral Hg(II) species (HgCl2, HgClOH, and Hg(OH)2) can occur with amino and oxygen-containing functional groups on the PEI-CMC beads. Considering species distribution of Hg(II) and the pHpzc of the PEI-CMC beads, electrostatic attraction between the positively-charged beads and anionic Hg(II) species (HgCl3− and HgCl42−) can take place in highly acidic solutions. The PEI-CMC beads were regenerated and reused for Hg(II) adsorption using 0.1 M HCl.

Optimization of Lead and Diclofenac Removal from Aqueous Media Using a Composite Sorbent of Silica Core and Polyelectrolyte Coacervate Shell.

The modification of inorganic surfaces with weak cationic polyelectrolytes by direct deposition through precipitation is a fast approach to generating composites with high numbers of functional groups. The core/shell composites present very good sorption capacity for heavy metal ions and negatively charged organic molecules from aqueous media. The sorbed amount of lead ions, used as a model for priority pollutants such as heavy metals, and diclofenac sodium salt, as an organic contaminant model for emerging pollutants, depended strongly on the organic content of the composite and less on the nature of contaminants, due to the different retention mechanisms (complexation vs. electrostatics/hydrophobics). Two experimental approaches were considered: (i) simultaneous adsorption of the two pollutants from a binary mixture and (ii) the sequential retention of each pollutant from monocomponent solutions. The simultaneous adsorption also considered process optimization by using the central composite design methodology to study the univariate effects of contact time and initial solution acidity with the purpose of enabling further practical applications in water/wastewater treatment. Sorbent regeneration after multiple sorption-desorption cycles was also investigated to assess its feasibility. Based on different non-linear regressions, the fitting of four isotherms (Langmuir, Freundlich, Hill, and Redlich-Peterson models) and three kinetics models (pseudo-first order (PFO), pseudo-second order (PSO), and two-compartment first order (TC)) has been carried out. The best agreement with experiments was found for the Langmuir isotherm and the PFO kinetic model. Silica/polyelectrolytes with a high number of functional groups may be considered efficient and versatile sorbents that can be used in wastewater treatment processes.

Adsorptive properties of highly porous activated carbon from açaí (Euterpe oleracea) towards the toxic herbicide atrazine

The great variety and possibilities of consumption of açaí pulp (Euterpe oleracea) have made its consumption increase considerably in recent years, mainly in Brazilian territory. The big problem is the generation of tons of waste that characterizes the fruit stone. This waste was converted into a highly porous activated carbon and employed to remove the herbicide atrazine. The characterization analyses confirmed that the applied methodology generated an adsorbent with good textural characteristics (specific surface area 920.56 m² g−1, pore volume 0.467 cm3 g−1; average pore diameter 1.13 nm). Furthermore, it was found that the adsorption of atrazine reached satisfactory results at natural pH and with an adsorbent mass of 0.54 g for each liter of solution. The Redlich-Peterson model presented the most satisfactory fit with the equilibrium data. This study found that the evolution of system temperature increased the concentration in the solid phase of 178 mg g−1 at 328 K. Regarding adsorption kinetics, the linear driving force model can represent the experimental data. Also, the predicted adsorption data of the model follows the experimental data. The application of the adsorbent in the removal of the herbicide mixture presented an efficiency of 81.45%. Therefore, using residual açaí fruit seeds as biomass for producing activated carbon employing zinc chloride as an agent activator is the possible application of the material. The material showed high efficiency and affinity with the target molecule.

Simple Co-Precipitation of Iron Minerals for the Removal of Phenylarsonic Acid: Insights into the Adsorption Performance and Mechanism.

In this study, three kinds of iron minerals, ferrihydrite, hematite, and goethite, were prepared by a simple coprecipitation method for the adsorption and removal of phenylarsonic acid (PAA). The adsorption of PAA was explored, and the influences of ambient temperature, pH, and co-existing anions on adsorption were evaluated. The experimental results show that rapid adsorption of PAA occurs within 180 min in the presence of iron minerals, and the adsorption process conforms to a pseudo-second-order kinetic model. The isothermal adsorption of PAA by ferrihydrite, goethite, and hematite agrees with the Redlich-Peterson model. The maximum adsorption capacities of PAA are 63.44 mg/g, 19.03 mg/g, and 26.27 mg/g for ferrihydrite, goethite, and hematite, respectively. Environmental factor experiments illustrated that an alkaline environment will significantly inhibit the adsorption of PAA by iron minerals. CO32-, SiO32-, and PO43- in the environment will also significantly reduce the adsorption performance of the three iron minerals. The adsorption mechanism was analyzed by FTIR and XPS, which indicated that ligand exchange between the surface hydroxyl group and the arsine group leads to the formation of an Fe-O-As bond, and electrostatic attraction between the iron minerals and PAA played an important role in the adsorption.

Bio-Based Polyurethane Foams for the Removal of Petroleum-Derived Pollutants: Sorption in Batch and in Continuous-Flow.

In this paper, we evaluated the potential of two synthesized bio-based polyurethane foams, PU1 and PU2, for the removal of diesel and gasoline from water mixtures. We started the investigation with the experiment in batch. The total sorption capacity S (g/g) for the diesel/water system was slightly higher with respect to gasoline/water, with a value of 62 g/g for PU1 and 65 g/g for PU2. We found that the sorption follows a pseudo second-order kinetic model for both the materials. The experimental data showed that the best isotherm models were obtained with Langmuir and Redlich-Peterson models. In addition, to provide an idea of the process scalability for future industrial applications, we tested the sorption capacity of the foams using a continuous-flow of the same oil/water mixtures and we obtained performances even better with respect to the batch test. The regeneration can be performed up to 50 times by centrifuge, without losing efficacy.

Highly efficient removal of toxic As(V), Cd (II), and Pb(II) ions from water samples using MnFe2O4@SBA-15-(CH2)3-adenine as a recyclable bio-nanoadsorbent

Millions of people nowadays are exposed to highly toxic ions, including arsenic, cadmium, and lead, which all have detrimental effects on human health and cause irreparable damage to the nature and health of living species. It is, therefore, absolutely crucial to remove these toxic ions from ecosystems. Herein, a sponge-like bio-nanocomposite with a core-shell-shell structure consisting of magnetic MnFe2O4 nanoparticles (NPs) as core and mesoporous silica (SBA-15) functionalized with the nucleobase adenine (Ade) as a shell was synthesized to be applied for the adsorptive removal of toxic ions from aqueous media. The prepared material was characterized using various techniques, such as FTIR, XRD, TEM, VSM, and BET. Under optimum conditions, the MnFe2O4@SBA-15@(CH2)3-Ade removed As(V), Cd(II), and Pb(II) ions with greater than 96% efficiency. The kinetic and equilibrium data were satisfactorily described by the pseudo-second-order and the Redlich-Peterson models. The maximum adsorption capacities for As(V), Cd(II), and Pb(II) were calculated to be 21.99 mg g−1, 29.62 mg g−1, and 31.01 mg g−1, respectively. Also, the bio-nanocomposite showed ion removal efficiencies of over 95% during the seventh cycle of adsorption-desorption. Pb (II) ions had a stronger affinity for the active sites of the bio-nanoadsrobent when all of the studied systems (mono-, bi-, and multi-component) were compared. In addition, the practical application of the bio-nanocomposite for ion capture was evaluated in groundwater and industrial wastewater samples. Based on the findings of this study, the MnFe2O4@SBA-15@(CH2)3-Ade can be considered a promising adsorbent for the fast and efficient removal of heavy metals from water matrices.