Enhanced sequestration of methylene blue and crystal violet dye onto green synthesis of pectin modified hybrid (Pect/AILP-Kal) nanocomposite

Investigating the adsorption processes of polymer resins for the removal of micropollutants: A comprehensive review in the field of environmental remediation

The growing worry for human health stems from the fact that micropollutants (MPs), particularly dyes, are more common in aquatic settings. These particles pose a serious risk to both humans and animals since they have been found in a variety of bodily fluids and waste products from both humans and animals. MPs pose significant dangers to human health and other living things due to their extended half-lives, high fragmentation propensity, and capacity to absorb organic pollutants as well (MB, MR, MO and CV dyes) and heavy metals as well (Pb(II), Cd(II) Co(II) Cr(III) and Ag(I) ….). They also contribute to the degradation of terrestrial and aquatic habitats. Sustainable and effective methods for removing MPs from wastewater and treating organic micropollutants in an environmentally friendly manner are being developed in order to address this problem. This work offers a thorough review of adsorption technology as a productive and environmentally friendly means of eliminating MPs from aqueous environments, with an emphasis on developments in the application of polymeric resin in MP removal. The review examines the adsorption process and the variables that affect adsorption efficiency, including the characteristics of the micropollutant, the resin, and the solution. To improve understanding, a number of adsorption mechanisms and models are explored. The study also addresses the difficulties and future possibilities of adsorption technology, emphasising the need to optimize resin characteristics, create sustainable and affordable regeneration techniques, and take into account the environmental effects of adsorbent materials.

Exploring the potential of waste biomass-derived pectin and its functionalized derivatives for water treatment

Environmental pollution remains a constant challenge due to the indiscriminate use of fossil fuels, mining activities, chemicals, drugs, aromatic compounds, pesticides, etc. Many emerging pollutants with no fixed standards for monitoring and control are being reported. These have adverse impacts on human life and the environment around us. This alarms the wastewater management towards developing materials that can be used for bulk water treatment and are easily available, low cost, non-toxic and biodegradable. Waste biomass like pectin is extracted from fruit peels which are a discarded material. It is used in pharmaceutical and nutraceutical applications but its application as a material for water treatment is very limited in literature. The scientific gap in literature review reports are evident with discussion only on pectin based hydrogels or specific pectin derivatives for some applications. This review focuses on the chemistry, extraction, functionalization and production of pectin derivatives and their applications in water treatment processes. Pectin functionalized derivatives can be used as a flocculant, adsorbent, nano biopolymer, biochar, hybrid material, metal-organic frameworks, and scaffold for the removal of heavy metals, ions, toxic dyes, and other contaminants. The huge quantum of pectin biomass may be explored further to strengthen environmental sustainability and circular economy practices.

Enhancing basil essential oil microencapsulation using pectin/casein biopolymers: Optimization through D-optimal design, controlled release modeling, and characterization

A D-optimal design was employed to optimize the microencapsulation (MEC) of basil essential oil (BEO) within a biopolymer matrix using the complex coacervation technique. BEO microcapsules (BEO-MCs) obtained under the optimal conditions exhibited high yield and efficiency with 80.45 ± 0.01 % and 93.10 ± 0.18 %, respectively. The successful MEC of BEO with an average particle size of 4.81 ± 2.86 μm was confirmed by ATR-FTIR, X-RD, and SEM analyses. Furthermore, the thermal stability of BEO-MCs was assessed using TGA-DSC analysis, which provided valuable insights into the MC's thermal stability. Furthermore, the proposed model, with a high R2 value (0.99) and low RMSE (1.56 %), was the most suitable one among the tested models for the controlled release kinetics of the optimal BEO-MCs under simulated gastrointestinal conditions. The successful optimization of BEO MEC using biopolymers through the D-optimal design could be a promising avenue for food and pharmaceutical industries, providing new strategies for the development of effective products.

Removal of cationic dyes from aqueous solution using polyacrylic acid modified hemp stem

Water pollution caused by dyes is a pressing environmental challenge due to their persistence and difficulty in degradation. Herein, an anionic adsorbent (HS-PAANa) was synthesized by grafting polyacrylic acid (PAA) onto the agricultural waste-hemp stem (HS). The obtained HS-PAANa adsorbent exhibited rapid adsorption kinetics, high adsorption capacity, and a favorable preference for cationic dyes, such as methylene blue (MB) and crystal violet (CV). The experimental data fit well with the pseudo-second-order kinetic model and Langmuir isotherm, demonstrating the efficiency of HS-PAANa in dye removal. Notably, the optimal adsorption capacities of HS-PAANa for MB and CV were found to be 1296.65 mg/g and 1451.43 mg/g, respectively. In the cationic/anionic dyes (MB/MO) binary systems, HS-PAANa exhibited enhanced selective adsorption of cationic dyes (MB), indicating its potential for targeted removal of specific dyes from mixed solutions. Moreover, HS-PAANa adsorption shows an excellent recyclability, after five cycles, HS-PAANa still maintained MB and CV removal rates of 93.85% and 95.08%, respectively. Therefore, the bioadsorbent HS-PAANa exhibits high potential as a highly efficient adsorbent for the effective treatment of cationic pollutants in wastewater.

Sponge-like biodegradable polypyrrole-modified biopolymers for selective adsorption of basic red 46 and crystal violet dyes from single and binary component systems

Recently, several researchers have been trying to reduce the ecological effects of water pollution by considering the use of biodegradable materials that prevent the generation of secondary pollution in our environment and enable water reuse. Here, new biodegradable hydrogels based on alginate (Alg), gelatin (Gel) and polypyrrole (PPy) were successfully implemented to remove two known highly toxic cationic dyes from wastewater. The design process was performed in two steps: in-situ polymerization of polypyrrole within the Alg/Gel mixture, followed by hydrogel formation. Biocomposites showed promising efficacy for the removal of both basic red 46 (BR46) and crystal violet (CV) dyes from real and demineralized water samples. However, Alg-Gel-PPy hydrogel showed better selectivity for BR46 than for CV as compared to the pristine Alg-Gel hydrogel. Adsorption of both pollutants on biocomposite hydrogel beads followed the Langmuir isotherm and pseudo-second order kinetic models. Besides, the highest adsorption capacities (125 mg g-1 for BR46 and 88.5 mg g-1 for CV) were obtained for the Alg-Gel-PPy hydrogel, compared with those determined for PPy-free hydrogel (103.09 mg g-1 for BR46 and 86.96 mg g-1 for CV) and remained at a satisfactory level for five adsorption-desorption cycles. Finally, the obtained hydrogels showed excellent biodegradability by natural soil microorganisms, with 91 % decomposition.

Optimization of an experimental study of cationic Pb metal adsorption by resin polymer

To eliminate lead (Pb) ions from metallic solutions, the cationic resin in solid form was utilized. The characterization of the adsorbent was performed using GTA/GTD, SEM spectroscopy, and EDX analysis. The results of these analyses provided insights into the structure and composition of the resin. The removal of Pb (II) ions was found to be highly dependent on various parameters. Firstly, the pH of the metal solution played a crucial role, as the adsorption capacity increased with the pH of the solution, at a maximum equal to (R = 84.78%), at a pH = 8.0. Additionally, the concentration of Pb (II) ions present in the solution influenced the adsorption technique's capacity, with higher concentrations leading to increased adsorption, analysis overhead of high concentration present (100 mg L-1) of the metal lead (II) study, a saturation corresponding a plateau to the resin polymeric saturation is 93.18 mg g-1. To determine the optimal mass of the resin adsorbent, a study was conducted to maximize the removal of Pb (II) ions, at the mass 1.0 g showed that the proportion of inorganic pollutants removed from Pb (II) is entirely qualitative (100%). Furthermore, the effect of temperature on the adsorption process was investigated. It was observed that the rate of the Pb (II) adsorption process decreased as the temperature increased. Kinetic studies were performed to gain further insights into the adsorption process. Pseudo-first-order and pseudo-second-order models, along with the intra-particle diffusion model, were utilized for this purpose. The results indicated that the adsorption process was fast, as evidenced by the findings from the pseudo-second-order study. The saturation technical process was studied, employing several different isothermal models, including Langmuir, Freundlich, and Temkin. Among these models, the Langmuir model was found to best describe the phenomenon of lead metal adsorption by the resin polymeric, is equal to 11.23 mg g-1, with the experimental value precisely (R2 = 0.999). Finally, various thermodynamic techniques were applied to analyze the adsorption process. The thermodynamic parameters such as ΔG° (- 9.78 to - 9.27 kJ mol-1), ΔH° (14.85 kJ mol-1), and ΔS° (0.017 kJ mol-1) were determined. These values indicated that the adsorption process was endothermic and spontaneous, further emphasizing its impetuous nature. The results of the molecular dynamics calculations demonstrated that amino groups are very important in defining the characteristics of cation adsorption. We conclude that this new adsorbent has the potential to significantly improve the process of regularly removing heavy metal ions from wastewater.

β-cyclodextrin grafted multi-walled carbon nanotubes/chitosan (MWCNT/Cs/CD) nanocomposite for treatment of methylene blue-containing aqueous solutions

β-cyclodextrin (CD) was grafted with multi-walled carbon nanotubes/chitosan (MWCNTs/Cs) to obtain MWCNTs/Cs/CD nanocomposite (NC) for methylene blue (MB) adsorption from aqueous media. TEM, XRD, TGA, Raman spectra, and BET & BJH analyses were utilized to characterize and confirm the successful synthesis of as-prepared NC. MB capture was investigated by considering the parameters of pH (1.9-9.0), temperature (∼16-63 °C), sonication time (∼5-15 min), MB concentration (∼1.2-48 mg/L), and NC dose (0.03-0.26 mg). The obtained responses were then modelled using CCD, generalized regression neural network (GRNN), and least squares support vector machine (LS-SVM), of which the latter found to provide most reliable and accurate results (RMSE = 0.0235, MAE = 0.020, AAD = 0.0047, and R2 = 0.999). Moreover, the genetic algorithm-based optimization results showed that under the respective values of 7.05, 45.5 °C, 10 min, 23 mg/L, 0.12 g, MWCNTs/Cs/CD NC would be able to remove 96.75% of MB with an adsorption capacity of 603 mg/g, through different mechanisms mainly electrostatic interactions. Following from Dubinin-Radushkevich (D-R) isotherm (qs = 460.66 ± 8.9 and R2 > 0.99) and intraparticle diffusion kinetic (R2 = 0.75-0.90) models indicated a chemical adsorption mechanism. Besides, thermodynamic parameters (ΔH◦ = -66.9 kJ/mol, ΔG◦ = between -3.77 kJ/mol and -8.52 kJ/mol, and ΔS◦ = 237.1818 J/mol K) confirmed an endothermic and spontaneous nature for the adsorption. These findings along with appropriate recyclability (five times), turn the as prepared NC to a promising material in removing MB from aqueous solutions.

Development and optimization of geopolymer adsorbent for water treatment: Application of mixture design approach

The current paper refers to the study of a new approach to optimizing the adsorptive properties of geopolymers by varying the aluminosilicate precursors from kaolin (K), metakaolin (MK), and coal fly ash (CFA) as internal synthesis factors. The simplex-augmented-centroid mixture design was applied to identify the optimal formulation from the three aluminosilicate precursors to develop a geopolymer (GP) with a distinctive structure that positively affects its dye adsorption efficiency. The variously formulated GP samples were tested for the removal of both methylene blue (MB-dye) and crystal violet dye (CV-dye) from an aqueous solution. The mathematical-statistical analysis of the experimental readings suggested that the generated special cubic models were significant, and thus the chosen approach was adequate for determining the optimum blending proportion. The optimization tools indicated that the optimal mixture from the three aluminosilicate precursors for developing a GP with high adsorption efficiency was 58% MK, 42% K, and 0% CFA. The optimized geopolymer (GP_O) was synthesized and then analyzed using a variety of physicochemical techniques, which revealed the presence of an amorphous N-A-S-H gel-rich porous structure as an influencing property on the geopolymer's organic dye adsorption efficiency. The dependence of the adsorption mechanism of both MB-dye and CV-dye by GP_O on the adsorbent dosage, contact time, initial dye concentration, temperature, and solution pH was evaluated. The isothermic and kinetic experimental readings for MB and CV-dyes adsorption by GP_O were well fitted to the pseudo-second-order and Freundlich models, with an exothermic, favorable, and spontaneous adsorption reaction thermodynamically. The experimental studies in the lab scale on GP_O produce comparable results. From these results, it has been concluded that the accuracy and feasibility of the mixture design simulation succeeded in optimizing and developing a geopolymeric sorbent material with great potential as an excellent economical agent for removing cationic dyes from aqueous media. This point represents an added value compared to traditional non-optimized geopolymer absorbents. Besides, this geopolymer material represents a significant application possibility for water treatment and remediation of hazardous dye pollutants.

Physico-chemical, structural, and adsorption properties of amino-modified starch derivatives for the removal of (in)organic pollutants from aqueous solutions

In this study, an environmentally sustainable process of crystal violet, congo red, methylene blue, brilliant green, Pb²⁺, Cd²⁺, and Zn²⁺ ions adsorption from aqueous solutions onto amino-modified starch derivatives was investigated. The degree of substitution, elemental analysis, swelling capacity, solubility, and FTIR, XRD, and SEM techniques were used to characterize the adsorbents. The influence of pH, contact time, temperature, and initial concentration has been studied to optimize the adsorption conditions. The amino-modified starch was the most effective in removing crystal violet (CV) (65.31-80.46 %) and Pb²⁺ (67.44-80.33 %) within the optimal adsorption conditions (pH 5, 10 mg dm^-3, 25 °C, 180 min). The adsorption of CV could be described by both Langmuir and Freundlich adsorption isotherms, while the adsorption of Pb²⁺ ions was better described by the Langmuir isotherm. The pseudo-second order model can be used to describe the adsorption kinetics of CV and Pb²⁺ on all tested samples. The thermodynamic study indicated that the adsorption of CV was exothermic, while the Pb²⁺ adsorption was endothermic. The simultaneous removal of CV and Pb²⁺ from the binary mixture has shown their competitive behavior. Thus, the amino-modified starch is a promising eco-friendly adsorbent for the removal of dyes and heavy metals from polluted water.

Reduced Graphene Oxide-Modified Spinel Cobalt Ferrite Nanocomposite: Synthesis, Characterization, and Its Superior Adsorption Performance for Dyes and Heavy Metals

This work is dedicated to the synthesis, characterization, and adsorption performance of reduced graphene oxide-modified spinel cobalt ferrite nanoparticles. The as-synthesized reduced graphene oxide cobalt ferrite (RGCF) nanocomposite has been characterized using FTIR spectroscopy, FESEM coupled with EDXS, XRD, HRTEM, zeta potential, and vibrating sample magnetometer (VSM) measurements. FESEM proves the particle size in the range of 10 nm. FESEM, EDX, TEM, FTIR, and XPS analyses provide the proof of successful incorporation of rGO sheets with cobalt ferrite nanoparticles. The crystallinity and spinel phase of cobalt ferrite nanoparticles have been shown by XRD results. The saturation magnetization (M _s) was measured as 23.62 emu/g, proving the superparamagnetic behavior of RGCF. The adsorption abilities of the synthesized nanocomposite have been tested using cationic crystal violet (CV) and brilliant green (BG) and anionic methyl orange (MO) and Congo red (CR) dyes. The adsorption trend for MO, CR, BG, and As(V) follows RGCF > rGO > CF at neutral pH. Adsorption studies have been accomplished by optimizing parameters like pH (2-8), adsorbent dose (1-3 mg/25 mL), initial concentration (10-200 mg/L), and contact time at constant room temperature (RT). To further investigate the sorption behavior, isotherm, kinetics, and thermodynamic studies have been conducted. Langmuir isotherm and pseudo-second-order kinetic models suited better for the adsorption of dyes and heavy metals. The maximum adsorption capacities (q _m) obtained have been found as 1666.7, 1000, 416.6, and 222.2 mg/g for MO, CR, BG, and As, respectively, with operational parameters such as T = 298.15 K; RGCF dose: 1 mg for MO and 1.5 mg each for CR, BG, and As. Thus, the RGCF nanocomposite was found to be an excellent adsorbent for the removal of dyes and heavy metals.

Multifunctional Ternary NLP/ZnO@l-cysteine-grafted-PANI Bionanocomposites for the Selective Removal of Anionic and Cationic Dyes from Synthetic and Real Water Samples

The development of competent adsorbents based on agro-waste materials with multifunctional groups and porosity for the removal of toxic dyes from aqueous solutions is still a challenge. Herein, a bionanocomposite made up of neem leaf powder (NLP), zinc oxide (ZnO), and amino acid (l-cysteine)-functionalized polyaniline (PANI), namely, NLP/ZnO@l-cysteine-grafted-PANI (NZC-g-PANI), has been prepared by an in situ polymerization method. The as-prepared bionanocomposite was tested for the adsorptive removal of three anionic dyes, namely, methyl orange (MO), amido black 10B (AB 10B), and eriochrome black T (EBT), as well as three cationic dyes, namely, brilliant green (BG), crystal violet (CV), and methylene blue (MB), from synthetic aqueous medium. The morphological and structural characteristics of the NZC-g-PANI nanocomposite were examined with the help of HR field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopy. FTIR and Raman studies show that the formulated NZC-g-PANI have an ample number of functional moieties such as carboxyl (-COOH), hydroxyl (-OH), amines (-NH₂), and imines (-N=), thus demonstrating outstanding dye removal capacity. C-S linkage helps to attach l-cysteine with polyaniline. Moreover, the predominance of chemisorption via ionic/pi-pi interaction and hydrogen bonding between the NZC-g-PANI nanocomposite and dyes (BG and MO) has been realized by FTIR and fitting of kinetics data to the PSO model. For both BG and MO dyes, the biosorption isotherm was precisely accounted for by the Langmuir isotherm with q _max values of up to 218.27 mg g^-1 for BG at pH 6 and 558.34 mg g^-1 for MO at pH 1. Additionally, thermodynamic studies revealed the endothermic and spontaneous nature of adsorption. NZC-g-PANI showed six successive regeneration cycles for cationic (MO: from 96.3 to 90.4%) and anionic (BG: from 94.7 to 88.7%) dyes. Also, batch adsorption operations were validated to demonstrate dye biosorption from real wastewater, such as tap water, river water, and laundry wastewater. Overall, this study indicates that the prepared NZC-g-PANI biosorbent could be used as an effective adsorbent for the removal of various types of anionic as well as cationic dyes from different aqueous solutions.

Competitive adsorption of nitrate, phosphate, and sulfate on amine-modified wheat straw: In-situ infrared spectroscopic and density functional theory study

Amine-modified wheat straw (AMWS) has already been reported as a promising adsorbent for nitrate (NO₃) removal due to its cost-effectiveness and high efficiency. However, the NO₃ removal mechanism has not been well understood, especially in the presence of co-existing ions. Here, the effect of co-existing anions on NO₃ removal by AMWS was investigated and the underlying mechanisms were revealed using a combination of in-situ infrared (IR) spectroscopy and computational modeling. The in-situ IR results indicated that NO₃, sulfate (SO₄), and phosphate (PO₄) are all adsorbed as outer-sphere complexes on AMWS. The two-dimensional-correlation spectroscopy analysis implied the adsorption sequence of SO₄ > PO₄ > NO₃. The adsorption energies obtained from density functional theory calculation range from -0.24 to 0.51 eV (-23.2 to 49.2 kJ/mol), confirming that these anions adsorb on AMWS as outer-sphere complexes. For the first time, this study provides direct spectroscopic evidence of the outer-sphere adsorption of NO₃ on AMWS, as well as identifies the adsorption sequence, confirmed by computational modeling. The competitive mechanism of NO_3, SO₄, and PO₄ revealed in this study is helpful to understand and predict the applications of AMWS.

Innovative adsorbents based on bentonite mining waste for removal of cationic dyes from wastewater

Waste rock from bentonite mining (WRBM) was evaluated as potential adsorbents for removing crystal violet (CV) and methylene blue (MB) cationic dyes from contaminated water. The waste samples (AM01, AM02, and AM03) were collected from different locations of the bentonite mine and characterized through X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy, N₂ adsorption/desorption, and cation exchange capacity. The adsorption efficiency of CV and MB dyes was investigated through the effect of initial concentration, contact time, pH, the dosage of adsorbent, and temperature. Sample AM02 showed the largest surface area (69.13 m²/g) and the best adsorptive performance for both dyes, with removal more significant than 90%. The adsorption of CV and MB in the waste followed the Langmuir isothermal model. Samples AM01 and AM02 followed the pseudo-second-order (PSO) kinetic model, while AM03 better fitted the Elovich kinetic model. The enthalpy (ΔH), entropy (ΔS), and Gibbs energy (ΔG) were evaluated as adsorption parameters. The process of adsorption of CV and MB dyes in the waste was predominantly endothermic and occurred spontaneously. WRBM samples proved to be a promising candidate for removing cationic dyes present in water.

Synthesis of high surface area mesoporous ZnCl2–activated cocoa (Theobroma cacao L) leaves biochar derived via pyrolysis for crystal violet dye removal

Chemically activated cocoa leaves biochar (CLB) was successfully prepared from fallen cocoa leaves (CLs) via ZnCl₂–activation and pyrolysis at 700 °C for sequestration of toxic crystal violet (CV) dye from aqueous solution. CLs and CLB were characterized using elemental analysis (CHN/O), Brunauer-Emmett-Teller method (BET), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), X-ray diffraction (XRD) spectroscopy and scanning electron microscopy (SEM). The optimum conditions for effective removal of CV dye from aqueous solution (75.67% for CLs and 99.87% for CLB) were pH 9, initial CV dye concentration 100 mg/L, adsorbent (CLs/CLB) dose 0.4 g/L, contact time 160 min and temperature 300 K. Modified Ritchie second order best described kinetic and Liu model described equilibrium adsorption. CLs and CLB with maximum adsorption capacities 190.70 and 253.3 mg/g respectively, compete favorably with adsorbents used for removal of CV dye from wastewater in the literature. The high BET surface area (957.02 m²/g) and mean pore diameter (7.21 nm) were indicators of better adsorption efficiency of CLB. CLs showed adsorption to proceed towards endothermic process, while it was exothermic process for CLB. This study established the suitability of cocoa leaves as sustainable and environmental friendly precursor for preparation of adsorbent for the treatment of dye-containing wastewater.

Removal of p-Nitrophenol from simulated sewage using steel slag: Capability and mechanism

The steel slag was investigated for the removal of p-nitrophenol (4-NP) from simulated sewage by batch adsorption and fixed-bed column absorption experiments. The results showed that the maximum adsorption capacity was 109.66 mg/g at 298 K, pH of 7, initial concentration 100 mg/L, and dose 0.8 g/L. The adsorption process fitted the Langmuir isothermal adsorption model and followed pseudo-second-order kinetic models, the activation energy of adsorption (Ea) was 10.78 kJ/mol, which indicated that the adsorption was single-molecule layer physical adsorption. The regeneration efficiency was still maintained at 84.20% after five adsorption-desorption cycles. The column adsorption experiments showed that the adsorption capacity of the Thomas model reached 13.69 mg/g and the semi-penetrating time of the Yoon-Nelson model was 205 min at 298 K. Fe₃O₄ was identified as the main adsorption site by adsorption energy calculation, XRD and XPS analysis. The FT-IR, Zeta potential, and ionic strength analysis indicated that the adsorption mechanism was hydrogen bonding interaction and electrostatic interaction. This work proved that steel slag could be utilized as a potential adsorbent for phenol-containing wastewater treatment.

Application of calcium alginate-PANI@sawdust wood hydrogel bio-beads for the removal of orange G dye from aqueous solution

This work aims to investigate the adsorption performance of orange G (OG) dye from aqueous solutions employing PANI@sawdust biocomposite enrobed by calcium-alginate bio-beads (Alg-PANI@SD). The as-prepared adsorbent was characterized by scanning-electron-microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and Fourier transforms infrared (FT-IR) spectroscopy and used to remove orange G dye from aqueous water. Batch tests were performed as a function of adsorbent dosage, pH, contact time, interfering ions, and initial OG dye concentration. Experimental results show that the kinetic model of pseudo-first-order (PFO) and Freundlich isotherm perfectly fit the entire experimental data. Additionally, the prepared composite exhibited an excellent regeneration capacity and reusability for OG dye removal. The results revealed that the as-prepared Alg-PANI@SD bio-beads have the potential to be applied as a low-cost adsorbent for the adsorption of OG dye from aqueous media.

Fabrication of alginate@silver nanoparticles (Alg@AgNPs) bionanocomposite for the sequestration of crystal violet dye from aqueous solution

In the present study, alginate@silver nanoparticles (Alg@AgNPs) bionanocomposite has been fabricated successfully and further explored for the removal of crystal violet (CV) dye from the aqueous solution. The surface morphology of the (Alg@AgNPs) bionanocomposite was characterized by various modern analytical techniques such as SEM-EDX, TEM, FTIR and XRD. The maximum adsorption was observed at optimum condition of (pH 7, adsorbent dose 0.01 g, equilibrium time 240 min and initial concentration 20 mg L^-1). The maximum monolayer adsorption capacity was found to be 186.93 mg g^-1 at 30 °C. The experimental data were further validated by various isotherm models and on the basis of highest correlation coefficient (R², 0.99), Langmuir model was found to be best fitted model. Pseudo-second order kinetic model obeyed best for the experimental data with a highest correlation coefficient (R², 0.99) at all studied temperature. In thermodynamic studies, the positive value of enthalpy change (∆H⁰) and entropy change (∆S⁰) confirmed the process to be endothermic and spontaneous in nature. Desorption studies shows that 83 % of the adsorbed CV can be desorbed in first cycle and can be regenerated up to 4th cycle effectively with 0.1 M HCl. Therefore, (Alg@AgNPs) bionanocomposite could be harnessed as a potential adsorbent for the removal of hazardous CV dye from the waste water.

Lignin grafted hydroxyapatite entrapped in polyacrylamide: Characterization and adsorptive features for Th4+ and bovine serum albumin

Water-soluble sulfolignin (SL) was grafted onto hydroxyapatite (Hap) by using epichlorohydrin. SLgHap was then entrapped in cross-linked polyacrylamide by in situ polymerizations of acrylamide and N, N'-methylenebisacrylamide to obtain the composite of PSLgHap. The composite was characterized by FT-IR, BET- porosity, XRD, EDXRF, SEM-EDX, TGA-DTG, PZC, CEC, and swelling tests. The adsorptive features of PSLgHAP were investigated for Th⁴⁺ and BSA in view of its dependence on pH, ionic intensity, concentration, temperature, and time. The results of characterization tests confirmed the formation of PSLgHap. The grafting efficiency concerning sulfur contents of PSLgHap was 96% by EDXRF. The isotherms were best represented by the Sips model, Langmuir adsorption capacities were 369 and 390 mg g_SLgHap^-1 for BSA and Th⁴⁺. The enthalpy and entropy changes were positive whilst Gibbs energy was negative by entropy controlled. The adsorption kinetics of both species was obeyed to pseudo second-order model, whereas it was first-order for BSA and hybrid-order for Th⁴⁺ of Langmuir model.