Kinetics, isotherms, and mechanism of removing cationic and anionic dyes from aqueous solutions using chitosan/magnetite/silver nanoparticles

Novel chitosan-magnetite-silica ternary capsules for highly efficient sequestration of reactive dyes from aqueous media

The main goal of this study was to synthesize novel Chitosan Magnetite Silica (CMS) adsorbent capsules and apply them for effective sequestration of anionic dyes Remazol brilliant blue 19 (RB-19) and Remazol golden yellow G -17 (RY-17) dye. The CMS capsules were synthesized and applied for batch study and evaluated using statistical modelling. Various analytical techniques, such as Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), Thermogravimetry-Differential Thermal Analysis (TG-DTA), Brunauer-Emmett-Teller (BET) surface area analysis, UV-Vis Spectrophotometry, and Vibrating Sample Magnetometry (VSM), were employed to validate the formation of the CMS. Rough surface as shown by SEM analysis, presence of various functional groups as shown by FT-IR spectrum and presence Fe atoms in EDX spectrum are indication of formation of complete composite. The surface area of CMS recorded by BJH method was 39.05 m2 g-1 with pore capacity 0.259 cm3 g-1. According to IUPAC classification, class IV isotherm was observed for nitrogen adsorption-desorption curves. The specific magnetization of CMS was 4.28 emu g-1 indicating fare degree of magnetism making it easily separable using external magnet. Batch trails as well as screening experiments were conducted for the sequestration of RB and RY dyes. Dose 50 mg, interface time 60 min and solution pH of 3.0 depicted maximum removal efficacy of more than 95 % in both dyes even at high initial concentration of 200 mg L-1. The adsorption capacities for RB-19 dye and RY-17 dye were found to be 455.86 and 344.06 mg g-1 respectively in accordance with pseudo second order kinetics (R2 = 0.997 and 0.962 respectively) and Langmuir adsorption isotherm (R2 = 0.972 and 0.992 respectively) models. Six adsorption-desorption cycles were conducted for regeneration potential of CMS showcasing repeated usability after regeneration in alkaline medium. E-factor value of 0.04 depicted CMS capsules was sustainable in and eco-friendly with low waste generation.

Biogenic nano-silver doped grapefruit peels biocomposite for biosorptive photocatalytic degradation of organic pollutants

In the present study a novel biogenic nano-silver doped grapefruit peels biocomposite (GFP@Ag) has been synthesized in a single-step procedure. The GFP@Ag nano-biocomposite was characterized using UV Visible spectrophotometer, Fourier Transform infrared (FTIR), scanning electron microscopy (SEM), (EDS), Thermogravimetric analysis (TGA), Proton nuclear resonance (1HNMR), and N2 adsorption desorption isotherm (BET). A combined approach of photocatalysis and biosorption is involved for the Toluidine blue O (TO), Crystal violet (CV), and brilliant green (BG) cationic dyes utilizing GFP@Ag biocomposite at pH (4-8). The investigated dye concentration was (100-200 ppm) with contact time (20-120 min) and 0.005 g of GFP@Ag at 25 °C under visible sunlight. The maximum degradation-biosorption capacities were 194.8 mg/g, 390.6 mg/g, and 306 mg/g for TO, CV, and BG, respectively. It was concluded that the TO, CV, and BG experimental data matched the pseudo-2nd -order (PSO) and Langmuir models from the kinetic and isotherm studies, respectively. The GFP@Ag was successfully applied to remove TO, CV, and BG multi systems (binary & tertiary). It was concluded that from the thermodynamics investigation, the current photocatalytic-biosorption processes are spontaneous and endothermic. The investigation was extended to estimate a straightforward and environmentally friendly method of producing silver nanoparticles that was able to overcome the drawbacks of alternative methods. Moreover, the evaluation of the applicability of GFP@Ag for the TO, CV, and BG removal in water samples was obtained. The GFP@Ag can be regenerated after the TO removal. The mechanism of the degradation-biosorption of the pollutants under study is elucidated.

Polyethylenimine-grafted cellulose nanofibril composites: Adsorbents for anionic dye removal with thermodynamic insights

Water pollution is a critical environmental issue that necessitates innovative approaches to water purification. This study presents the development of a novel cellulose-based adsorbent, DCNF/PEI, synthesized by grafting branched polyethyleneimine (PEI) onto dialdehyde cellulose nanofibers (DCNF) via a Schiff base reaction. This functionalization enhances the adsorption capacity of cellulose nanofibers for removing anionic dyes from aqueous solutions. The DCNF/PEI composite was characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and Thermogravimetric Analysis (TGA), confirming successful modification and favorable structural and thermal properties. Batch adsorption experiments with methyl orange (MO) were conducted under various conditions, including pH, dye concentration, and contact time. The composite exhibited excellent dye removal efficiency, achieving a maximum adsorption capacity of 313 mg/g. The adsorption process followed the Langmuir isotherm and pseudo-second-order kinetic models, indicating monolayer chemisorption. These results highlight the DCNF/PEI composite as an efficient, sustainable, and scalable adsorbent for anionic dye removal, offering a promising solution for wastewater treatment.

Innovative nanocomposites for pollutant capture: Adsorption of rhodamine B dye using polyaniline-coated chitosan trisodium citrate nanocomposites

Wastewater contamination by organic dyes, especially Rhodamine B (RhB), possess a significant environmental challenge. This study explores a novel bio sorbent for the removal of RhB dye from contaminated water, using chitosan trisodium citrate-modified magnetic nanoparticles (Fe₃O₄@CSTSC@PANI) coated with polyaniline. The nanocomposite was characterized by FT-IR, XRD, HRTEM, SEM, BET surface analysis. The UV-visible spectroscopy was used to monitor the adsorption of dye on the nanocomposite. The Fe₃O₄@CSTSC@PANI nanocomposite exhibits a spherical core-shell morphology with a size range of 29-53 nm, a BET surface area of 13.099 m2/g, and high reusability. The pore area of the material increased from 0.8058 m2/g at 15.29 Å radius to 10.65 m2/g at 1310.89 Å, with a corresponding change in pore volume from 0.0006.16 cc/g to 0.0227 cc/g. This shows the significant contribution of the porous and mesoporous structures of polyaniline-coated chitosan trisodium citrate (nanocomposites) to the adsorption performance for pollutant capture such as Rhodamine B dye. Adsorption studies showed optimal RhB removal of 97.2 % at near neutral pH. Adsorption was most optimal at pH 6-9, with the highest efficiency near neutral pH, which facilitates electrostatic interactions. High temperature (10-70 °C) promoted the endothermic adsorption process, improving the dye uptake. The optimal adsorbent dosage (0.21-1.6 g/L) and equilibrium contact time (30-840 min) were determined. The nanocomposite material showed good recovery, maintaining high efficiency after 4 reuse cycles, demonstrating its practicality in sustainable environmental remediation. The adsorption mechanism was elucidated by isotherm and kinetic studies, which revealed that the process followed a pathway dominated by chemisorption facilitated by the interaction between polyaniline-coated chitosan nanocomposites and Rhodamine B dye molecules. This is the synergistic effect of electrostatic attraction, hydrogen bonding and π-π interactions, confirming the strong affinity of the mixture for the dye.

Biosorbent silver nanoparticles decorated coffee-ground waste composite for cleaning water and antimicrobial applications

A sustainable biosorbent, silver nanoparticles-decorated coffee-ground waste (CWAg), was synthesized through a simple in-situ reduction method. CWAg is extensively characterized via SEM-EDX, PZC, FTIR, XRD, HR-TEM, and XPS analyses. The biosorbent was tested to remove chromium (Cr(VI)) and methylene blue (MB) from wastewater, and its antibacterial properties was evaluated. CWAg demonstrated efficient sorption efficiencies, achieving ⁓149.9 mg/g at 323 K and pH: 2.0 for Cr(VI) and ⁓113.4 mg/g at 293 K and pH: 6.0 for MB, at a biosorbent dose of 1 g/L. The equilibration times were 90 and 120 min for Cr(VI) and MB, with half-sorption times (tHST) of 9.2 and 13.9 min, respectively. The sorption mechanisms were successfully fitted with Sips isotherm and Pseudo-second-order models. Simultaneous sorption of MB and Cr(VI) at pH 2.0 exhibited antagonism, while a synergistic effect was observed at pH 6.0. Desorption and regeneration were achieved using NaOH and HCl solutions for Cr(VI) and MB, respectively. The efficiencies were just reduced by 9-13%. Finally, CWAg exhibited remarkable effectiveness for removing Cr(VI) from complex tannery effluent. Moreover, CWAg demonstrated positive antibacterial effects against both Gram-positive and Gram-negative bacteria, surpassing raw coffee-ground waste, underscoring the significant role of silver nanoparticles in enhancing bacterial inhibition.

Facile fabrication of novel magnetic chitosan-alginate @ pomegranate peel extract nanocomposite for the adsorptive removal of naphthalene from aqueous solutions

The prevalent presence of naphthalene contamination in aquatic ecosystems is a significant concern due to its carcinogenic and priority pollutant properties. This study focuses on the synthesis of magnetized chitosan/alginate/pomegranate peel extract nanocomposites (Fe3O4/PPE/Cs-Alg), was characterized by Zeta potential, vibrating sample magnetometer (VSM), Field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analyses. The results predicted that the successfully synthesis of Fe3O4/PPE/Cs-Alg. The study evaluates the efficacy of the nanocomposite in naphthalene removal, considering operational parameters like pH, varied initial naphthalene concentrations, nanocomposite doses and contact time . The maximum adsorption capacities of naphthalene optimal conditions were 88.12 mg/g for 50 ppm initial naphthalene concentration. The Langmuir, Freundlich, Temkin and Sips isotherms were applied to analyze the experimental equilibrium data. The Sips isotherm was identified as the most suitable model, as evidenced by the highest (R2 = 0.97), Also, the adsorption data conformed well to the pseudo-second-order kinetics model (R2 = 0.99). The thermodynamic study showed positive values for ΔH° and ΔS° throughout the adsorption process respectively, implying an endothermic behavior. Therefore, we found that it can significantly remove naphthalene in aqueous environments and hence could be useful for cleaning up the environment from Poly Aromatic Hydrocarbon.

Efficiency of CaZn₂(OH)₆·2H₂O and ZnO nanoparticles in photocatalytic degradation of amoxicillin after multiple cycles

The widespread use of antibiotics has increased their presence in wastewater, largely due to inadequate removal by conventional treatment methods. This highlights a critical need for effective degradation strategies to mitigate environmental and public health risks. This study reports the photocatalytic degradation of amoxicillin (AMX) using calcium zinc hydroxide dihydrate [CaZn2(OH)6·2H2O] (CZ) and zinc oxide (ZnO) nanoparticles (NPs) synthesized by different routes. X-ray diffraction results confirmed the formation of CZ NPs with an 81-95% crystalline phase, while ZnO NPs present a single crystalline phase. The photolysis of AMX under UV-A light (365 nm) was strongly pH-dependent, with degradation rates of 34.7, 5.7, and 4.2% observed at pH 3, 5, and 13, respectively. Maximum adsorption occurred at pH 3, with ZnO achieving 63-83.2% AMX removal and 23.5-47.1% in the case of CZ. The highest overall AMX removal was observed at pH 3, where adsorption dominated the photocatalytic process for both CZ and ZnO. At pH 5 and 13, degradation was primarily driven by photocatalysis in CZ materials, particularly CZ-HT and CZ-SG, while adsorption remained predominant in ZnO. Proton nuclear magnetic resonance analysis indicates benzene ring cleavage in AMX photodegraded by CZ materials. Furthermore, the residues of photodegraded AMX by CZ materials lost antimicrobial activity against Gram-positive and Gram-negative bacteria. Additionally, the reuse of NPs over four cycles maintained consistent degradation performance, highlighting their potential for repeated applications. The comparative analysis of CZ and ZnO NPs superior photocatalytic efficiency of CZ in degrading AMX. This efficiency, along with its potential for repeated use, establish CZ as a promising material for environmental applications aimed at reducing antibiotic contamination and the associated risks of resistance development.

High efficiency of treated-phengite clay by sodium hydroxide for the Congo red dye adsorption: Optimization, cost estimation, and mechanism study

Wastewater textile dye treatment is a challenge that requires the development of eco-friendly technology to avoid the alarming problems associated with water scarcity and health-environment. This study investigated the potential of phengite clay as naturally low-cost abundant clay from Tamgroute, Morocco (TMG) that was activated with a 0.1 M NaOH base (TMGB) after calcination at 850 °C for 3 h (TMGC) before its application in the Congo red (CR) anionic dye from the aqueous solution. The effect of various key operational parameters: adsorbent dose, contact time, dye concentration, pH, temperature, and the effect of salts, was studied by a series of adsorption experiments in a batch system, which affected the adsorption performance of TMG, TMGC, and TMGB for CR dye removal. In addition, the properties of adsorption kinetics, isotherms, and thermodynamics were also studied. Experimental results showed that optimal adsorption occurred at an acidic pH. At a CR concentration of 100 mg L-1, equilibrium elimination rates were 68%, 38%, and 92% for TMG, TMGC, and TMGB, respectively. The adsorption process is rapid, follows pseudo-second-order kinetics, and is best described by a Temkin and Langmuir isotherm. The thermodynamic parameters indicated that the adsorption of CR onto TMGB is endothermic and spontaneous. The experimental values of CR adsorption on TMGB are consistent with the predictions of the response surface methodology. These led to a maximum removal rate of 99.97% under the following conditions: pH = 2, TMGB dose of 7 g L-1, and CR concentration of 50 mg L-1. The adsorbent TMGB's relatively low preparation cost of around $2.629 g-1 and its ability to regenerate in more than 6 thermal calcination cycles with a CR removal rate of around 56.98%, stimulate its use for textile effluent treatment on a pilot industrial scale.

Surface modified of chitosan by TiO2@MWCNT nanohybrid for the efficient removal of organic dyes and antibiotics

Considering the increase in the discharge of industrial effluents containing dyes and antibiotic resistance as a consequence of increasing the prescription and easy distribution of antibiotic drugs at the global level, designing efficient, biodegradable and non-toxic absorbents is necessary to reduce environmental harm effects. Herein, we present a series of novel eco-friendly ternary hybrid nanocomposite hydrogels CS/TiO2@MWCNT (CTM) composed of chitosan (CS), TiO2, and multiwalled carbon nanotube (MWCNT) for removal of methylene blue (MB) and methyl orange (MO) and common antibiotic ciprofloxacin (CIP) in aqueous medium. The combination of MWCNT and TiO2 improves the physicochemical properties of CS hydrogel and increases the adsorption capacity toward pollutants in the presence of different loadings. CTM hydrogel showed a specific surface area of 236.45 m2 g-1 with a pore diameter of 7.89 nm. Adsorption mechanisms were investigated in detail using kinetic, isotherm, and thermodynamic studies of adsorption as well as various spectroscopic techniques. Adsorption of these pollutants by CTM nanocomposite hydrogel occurred using various interactions at different pHs, which showed the obvious dependence of CTM adsorption capacity on pH. Electrostatic attractions, complex formation, π-π stacking and hydrogen bonds played a key role in the adsorption process. The adsorption of MB, MO, and CIP was fitted with the Langmuir isotherm with maximum adsorption capacities of 531.91, 1763.6, and 1510.5 mg g-1, respectively. CTM had a minor decrease in adsorption strength and showed good structural stability even after 8 adsorptions-desorption cycles. The total cost of producing a 1 kg adsorbent was calculated to be $ 450, which helped us determine the economic feasibility of the adsorbent in large-scale applications.

Novel Chitosan-ZnO nanocomposites derived from Nymphaeaceae fronds for highly efficient removal of Reactive Blue 19, Reactive Orange 16, and Congo Red dyes

The primary aim of this investigation was to synthesise novel adsorbent by incorporating greenly synthesized zinc oxide nanoparticles into chitosan matrix (G-ZnO-Cs). The production of ZnO Nanoparticles via a green approach involved the utilization of extracts derived from Nymphaeaceae fronds. This assertion was substantiated by the application of Field Emission Scanning Electron Microscopy (FESEM) and X-ray Diffraction (XRD) analytical techniques. Several Analytical methods such as Fourier Transform Infrared spectroscopy (FT-IR), Energy Dispersive X-ray Analysis (EDAX), FESEM, Thermogravimetric Analysis (TGA), XRD, Brunauer-Emmett-Teller (BET) analysis, and point-of-zero charge determination were used to characterize G-ZnO-Cs. Further study investigates the impact of five key processing parameters, namely pH, interaction duration, G-ZnO-Cs dosage, temperature, and initial concentration of dyes, on the removal of three organic dyes Reactive Blue 19 (RB 19), Reactive Orange 16 (RO 16), and Congo Red (CR) The adsorption process of Reactive Blue 19 (RB 19), Reactive Orange 16 (RO 16), and Congo Red (CR) dyes on G-ZnO-Cs were determined to comply to the pseudo-second-order (PSO) and Langmuir models, as determined through equilibrium and kinetic experiments. The highest adsorption capabilities for RB 19, RO 16 and CR dye were revealed to be 219.6 mg/g, 129.6 mg/g, and 118.8 mg/g, respectively. The elimination success rate of the fixed-bed column approach for treating huge volumes was highlighted in the conducted research. Moreover, the G-ZnO-Cs composite exhibited significant reusability due to its ability to undergo elution and simultaneous regeneration processes.

Cellulose esters: Synthesis for further formation of films with magnetite nanoparticles incorporated

This study investigated the homogeneous synthesis of cellulose acetate (CA) and propionate (CP) with varying degrees of substitution (DS) from sisal cellulose in a N, N-dimethylacetamide/lithium chloride (DMAc/LiCl) solvent system. These esters were used to prepare neat (CADSF/CPDSF) and nanocomposite films (CADSFFe/CPDSFFe) from prior synthesized magnetite nanoparticles (NPs, Fe3O4, 5.1 ± 0.5 nm). Among the CA and CP series, the composite CA0.7FFe and the neat CP0.7F films exhibited the highest modulus of elasticity, 2105 MPa and 2768 MPa, respectively, probably a consequence of the continuous fibrous structures present on the surface of these films. Microsphere formation on the film's surface was observed in scanning electron microscopy micrographs. This points to applications in the controlled release of targeted substances. The VSM analysis showed that the cellulosic matrices preserved the superparamagnetic characteristics of the NPs. This study suggested a reduced coupling effect between nanoparticles inside polymeric films due to magnetic saturation at low fields. CA0.7FFe and CA1.3FFe composite films reached a saturation magnetization (MSAT) of 46 emu/g around 7 kOe field. Hosting magnetite nanoparticles in cellulose ester matrices may be an interesting way to develop new functional cellulose-based materials, which have the potential for diverse applications, including microelectromechanical systems and microsensors.

Production of eco-friendly adsorbent of kaolin clay and cellulose extracted from peanut shells for removal of methylene blue and congo red removal dyes

This present work targets the production of an eco-friendly adsorbent (hereinafter KA/CEL) from kaolin clay functionalized with cellulose extract obtained from peanut shells. The adsorbents were used for decolorization of two different types of organic dyes (cationic: methylene blue, MB; anionic: Congo red, CR) from an aqueous environment. Several analytical methods, including Brunauer-Emmett-Teller (surface properties), Fourier Transforms infrared (functionality), scanning electron microscope, Energy dispersive X-Ray (morphology), and pHpzc test (surface charge), were used to attain the physicochemical characteristics of KA/CEL. The Box-Behnken Design (BBD) was applied to determine the crucial factors affecting adsorption performance. These included cellulose loading at 25 %, an adsorbent dose of 0.06 g, solution pH set at 10 for MB and 7 for CR, a temperature of 45 °C, and contact times of 12.5 min for MB and 20 min for CR dye. The adsorption data exhibited better agreement with the pseudo-second-order kinetic and Freundlich models. The Langmuir model estimated the monolayer capacity to be 291.5 mg/g for MB and 130.7 mg/g for CR at a temperature of 45 °C. This study's pivotal finding underscores the promising potential of KA/CEL as an effective adsorbent for treating wastewater contaminated with organic dyes.

Endophytic Aspergillus hiratsukae mediated biosynthesis of silver nanoparticles and their antimicrobial and photocatalytic activities

In the current study, endophytic Aspergillus hiratsukae was used for the biosynthesis of silver nanoparticles (Ag-NPs) for the first time. The characterizations were performed using X ray diffraction (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX), Dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), and UV-Vis spectroscopy. The obtained results demonstrated the successful formation of crystalline, spherical Ag-NPs with particle diameters ranging from 16 to 31 nm. The FT-IR studied and displayed the various functional groups involved, which played a role in capping and reducing agents for Ag-NPs production. The SEM-EDX revealed that the main constituent of the AS-formed sample was primarily Ag, with a weight percentage of 64.2%. The mycosynthesized Ag-NPs were assessed for antimicrobial as well as photocatalytic activities. The antimicrobial results indicated that the synthesized Ag-NPs possess notable antibacterial efficacy against Staphylococcus aureus, Bacillus subtilis, and Escherichia coli, with minimum inhibitory concentrations (MICs) of Ag-NPs ranging from 62.5 to 250 μg/mL. Moreover, the biosynthesized Ag-NPs demonstrated weak antifungal activity against Aspergillus brasiliensis and Candida albicans, with MICs of 500 and 1,000 μg/mL, respectively. In addition, the mycosynthesized Ag-NPs exhibited photocatalytic activity toward acid black 2 (nigrosine) dye under both light and dark stimulation. Notably, After 300 min exposure to light, the nigrosine dye was degraded by 93%. In contrast, 51% degradation was observed after 300 min in darkness. In conclusion, Ag-NPs were successfully biosynthesized using endophytic A. hiratsukae and also exhibited antimicrobial and photocatalytic activities that can be used in environmental applications.

Citrate silver nanoparticles impregnated cellulose as a photocatalytic filter in the degradation of organic dye in the aqueous media

Photocatalysis is a clean and efficient process pursued under light irradiation with a suitable photocatalyst to degrade a contaminant. We report citrate functionalization of silver nanoparticles (SNPs) for effective immobilization on cellulosic fabric. The porous cellulosic matrix could be explored as microfiltration membranes for the photocatalytic degradation of organic dyes in the aqueous media. Where valid, the citrate functionalized SNPs and the treated cellulose fabrics were considered for optical, structural, surface chemical, thermal, textile, flowability, photocatalytic, and antibacterial attributes. The SNPs expressed the bandgap energy of 2.56 and 2.43 eV and Urbach energy of 3.38 and 5.21 eV before and after functionalization with the citrate moieties, respectively. The liquid chromatographic and FTIR analyses indicated that the crystal violet (CV) organic dye has been successfully photodegraded to environmentally safer and nontoxic species on passing the contaminated water through the SNPs-treated cellulosic filter. The spectroscopic data also supported the said outcomes. The results demonstrated that the citrate-SNPs-treated cellulose could be efficiently employed as antibacterial photocatalytic membranes for degrading organic dyes in the aqueous media for multiple cycles.

Flexible Synthesis of Bio-Hydroxyapatite/Chitosan Hydrogel Beads for Highly Efficient Orange G Dye Removal: Batch and Recirculating Fixed-Bed Column Study

The use of fish waste as a source material for the development of functional beads has significant potential applications in the fields of materials science and environmental sustainability. In this study, a biomaterial bead of chitosan was cross-linked with bio-hydroxyapatite (Bio-Hap/Cs) through the encapsulation process to create a stable and durable material. The beads are characterized using scanning electron microscopy combined with energy dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, and X-ray diffraction techniques. The adsorption efficiency of Bio-Hap/Cs hydrogel beads was evaluated by using Orange G (OG) dye in both batch and recirculating column systems, and the effect of various parameters on the adsorption capacity was investigated. In the batch study, it was found that OG removal increased with an increasing pH and adsorbent dose. However, in the recirculating column system, a higher bed height and lower flow rate led to increased removal of the OG dye. The kinetic study indicated that the pseudo-second-order model provided a good description of OG adsorption onto Bio-Hap/Cs beads in both batch and recirculating processes, with a high coefficient correlation. The maximum adsorbed amounts are found to be 19.944 mg g-1 and 9.472 mg g-1 in batch and recirculating processes, respectively. Therefore, Bio-Hap/Cs hydrogel beads have demonstrated an effective and reusable material for OG dye remediation from aqueous solutions using recirculating adsorption processes.

Design of chitosan/boehmite biocomposite for the removal of anionic and nonionic dyes from aqueous solutions: Adsorption isotherms, kinetics, and thermodynamics studies

This study introduces a chitosan/boehmite biocomposite as an efficient adsorbent for removing anionic Congo Red (CR) and non-ionic Bromothymol Blue (BTB) from water. Boehmite nanoparticles were synthesized using the Sol-gel method and then attached to chitosan particles using sodium tripolyphosphate through co-precipitation method. Characterized through FTIR, FE-SEM, BET, and XRD, the biosorbent displayed structural integrity with optimized pH conditions of 3 for CR and 4 for BTB, achieving over 90 % adsorption within 30 min. Pseudo second order kinetics model and Langmuir isotherm revealed monolayer sorption with capacities of 64.93 mg/g for CR and 90.90 mg/g for BTB. Thermodynamics indicated a spontaneous and exothermic process, with physisorption as the primary mechanism. The biosorbent demonstrated excellent performance and recyclability over five cycles, highlighting its potential for eco-friendly dye removal in contaminated waters.

An efficient multi-functional ternary reusable nanocomposite based on chitosan@TiO2@Ag NP immobilized on cellulosic fiber as a support substrate for wastewater treatment

To effectively remove heavy metals, organic contaminants, and pathogenic bacteria from wastewater, an efficient multi-functional ternary nanocomposite based on chitosan (CS), titanium dioxide (TiO2 NP), and silver nanoparticles (Ag NP) was prepared. Different tools were used to confirm the successful synthesis of the CS/TiO2 NP/Ag NP nanocomposite. Then, the CS/TiO2 NP/Ag NPnanocomposite was immobilized on the cellulosic fiber as a support substrate for its easy removal and reuse. On a lab scale, CS/TiO2 NP/Ag NP nanocomposite@cellulosic fiber was used to remove Cu (II) ions, methyl orange (MO), and methylene blue (MB), as well as inhibit microbes. The results demonstrate that the greatest removal of Cu (II) ions was 95 % at a concentration of 50 mg/L, pH 5, a temperature of 25 °C, an agitation speed of 200 rpm with 1 g adsorbent dose, and a contact time of 150 min. The pseudo-second-order model explained the batch adsorption kinetics well, while the Langmuir model explained the adsorption isotherm well with an adsorption capacity of 7.71 mg/g. Adsorption thermodynamic parameters revealed that adsorption is a spontaneous, exothermic, increased randomness, and non-specific chemisorption approach. The photodegradation of MO and MB by CS/TiO2 NP/Ag NP nanocomposite@cellulosic fiber was investigated. The results reveal that at pH 3, the MO dye showed the highest photodegradation percentage (90 %), while the MB dye displayed the highest photodegradation percentage (94 %) at pH 11, after an irradiation time of 120 min under visible light. The rate constants for MO and MB were 0.01218 and 0.01412 min-1, respectively. The results antimicrobial activities showed that the CS/TiO2 NP/Ag NP nanocomposite@cellulosic fiber showed excellent antibacterial activity against S. aureus (95 ± 2 %) and E. coli (93 ± 3 %) as well as good antifungal activity against C. albicans (77 ± 2 %).

Bisphenol-A-diglycidyl ether modified chitosan/nano-SiO2 via hydrothermal process: A statistical modeling and adsorption mechanism for reactive orange 16 dye removal

In this study, chitosan/nano SiO2 (CTS/NS) was chemically modified with bisphenol A diglycidyl ether (BADGE) cross-linker-assisted hydrothermal process to create an effective adsorbent, CTS-BADGE/NS, for the removal of reactive orange 16 (RO16) dye from aquatic systems. Box-Behnken design (BBD) was used to optimize the adsorption process by varying the adsorbent dose (0.02-0.1 g/100 mL), pH (4-10), and time (20-360 min). The adsorption isotherm results indicated that the Langmuir model fits the experimental data well, suggesting that the adsorption process involves a monolayer formation of RO16 on the surface of CTS-BADGE/NS. The kinetic modeling of RO16 adsorption by CTS-BADGE/NS demonstrated that the pseudo-first-order model fits the adsorption data. CTS-BADGE/NS achieved an adsorption capacity of 97.8 mg/g for RO16 dye at optimum desirability functions of dosage 0.099 g/100 mL, solution pH of 4.44, and temperature of 25 °C. Overall, the π-π electron donor-acceptor system significantly improved the adsorption performance of the CTS-BADGE/NS. The results of the regeneration investigation demonstrate that the CTS-BADGE/NS exhibits effective adsorption of RO16, even after undergoing five consecutive cycles. The results of this study suggest that the developed CTS-BADGE/NS composite can be a promising adsorbent for water purification applications.

Synthesis and characterization of Alg/Gel/n-HAP/MNPs porous nanocomposite adsorbent for efficient water conservancy and removal of methylene blue in aqueous environments: Kinetic modeling and artificial neural network predictions

In this study, a new porous nanocomposite adsorbent for water conservancy was synthesized using the freeze-drying technique to adsorb a cationic dye (Methylene Blue) in an aqueous environment. The nanocomposite adsorbent was synthesized using natural polymers, gelatin, and sodium alginate, and hydroxyapatite and magnetic iron oxide nanoparticles was incorporated into the polymer network to improve mechanical properties and increase the surface-to-volume ratio. To confirm the structure and morphology of the sample, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) techniques were employed. In addition, the magnetic properties of the synthesis of MNPs and porous nanocomposite were determined using value stream mapping (VSM) and dynamic light scattering (DLS). The adsorption of Methylene Blue (MB) was studied as a function of effective physical and variable parameters, such as time, temperature, pH, and initial concentration. The synthesized porous nanocomposite adsorbent exhibited a high adsorption capacity of 473.2 mg g-1 and followed pseudo-second-order kinetics. Additionally, the maximum adsorption capacity was observed at an initial concentration of 534.9 mg g-1. The adsorbent was also sensitive to temperature changes and was well-described thermodynamically and isothermally by the Freundlich isotherm model. Two artificial neural networks (ANNs) were also developed to investigate the properties of the synthesized nanocomposites. In the first ANN, the properties of the nanocomposites, including pore size, porosity, compressive strength, and elastic modulus, were predicted based on the variations in the weight percentages of gelatin and hydroxyapatite. In the second ANN, the effects of changes in temperature and initial concentration on the adsorption of MB by the synthesized nanocomposite samples were predicted. The ANNs' predictions indicated that increasing the weight percentage of hydroxyapatite nanoparticles and gelatin enhances the physical, mechanical, and adsorption performance of the synthesized porous nanocomposites. The best results were achieved for the sample containing 40 wt % of gelatin and 30 wt % of hydroxyapatite nanoparticles. Furthermore, the ANN models demonstrated that increasing the temperature and initial concentration resulted in an increase in the amount of MB adsorbed.

Magnetic biopolymers' nanocomposites from chitosan, lignin and phycosynthesized iron nanoparticles to remediate water from polluting oil

Targeting the remediation of oil pollution in water, the construction of super magnetic adsorbent nanocomposites (NCs) was achieved using the nanoparticles of chitosan (Cht), lignin (Lg) and phycosynthesized iron nanoparticles (Fe MNPs) using Gelidium amansii extract. The syntheses and conjugations of nanomaterials were authenticated via infrared spectral analysis and the structural physiognomies of them were appraised via electron microscopy and zeta analysis. The Lg NPs, Cht NPs, Fe MNPs and their composites (Lg/Cht MNCs) had mean particles' sizes of 42.3, 76.4, 14.2 and 108.3 nm, and were charged with - 32.7, + 41.2, + 28.4 and +37.5 mV, respectively. The magnetometer revealed the high magnetic properties of both Fe MNPs and Lg/Cht MNCs; the maximum swelling of Lg/Cht NPs (46.3 %), and Lg/Cht MNPs (33.8 %) was detected after 175 min. The diesel oil adsorption experiments with Lg/Cht MNPs, using batch adsorption practices, revealed the powerful potentiality of magnetic NCs to remove oil pollution in water; the maximum adsorption capacity (qt) was achieved with the conditions of pH = 7.5, adsorption period = 90 min and adsorbent dose = 200 mg/L. The magnetic Lg/Cht MNCs exhibited excellent recovery/reusability attributes for five adsorption cycles; the qt differences were negligible after the entire oil-adsorption cycles, with oil removal of >90 %. The innovative fabricated Lg/Cht MNCs could provide an effectual, sustainable and eco-friendly approach for the removal of pollutant oil in water resources.

Optimization of process parameters for trimethoprim and sulfamethoxazole removal by magnetite-chitosan nanoparticles using Box-Behnken design

The contamination of the aquatic environment with antibiotics is among the major and developing problems worldwide. The present study investigates the potential of adsorbent magnetite-chitosan nanoparticles (Fe3O4/CS NPs) for removing trimethoprim (TMP) and sulfamethoxazole (SMX). For this purpose, Fe3O4/CS NPs were synthesized by the co-precipitation method, and the adsorbent characteristics were investigated using XRD, SEM, TEM, pHzpc, FTIR, and VSM. The effect of independent variables (pH, sonication time, adsorbent amount, and analyte concentration) on removal performance was modeled and evaluated by Box-Behnken design (BBD). The SEM image of the Fe3O4/CS adsorbent showed that the adsorbent had a rough and irregular surface. The size of Fe3O4/CS crystals was about 70 nm. XRD analysis confirmed the purity and absence of impurities in the adsorbent. TEM image analysis showed that the adsorbent had a porous structure, and the particle size was in the range of nanometers. In VSM, the saturation magnetization of Fe3O4/CS adsorbent was 25 emu g-1 and the magnet could easily separate the adsorbent from the solution. The results revealed that the optimum condition was achieved at a concentration of 22 mg L-1, a sonication time of 15 min, an adsorbent amount of 0.13 g/100 mL, and a pH of 6. Among different solvents (i.e., ethanol, acetone, nitric acid, and acetonitrile), significant desorption of TMP and SMX was achieved using ethanol. Also, results confirmed that Fe3O4/CS NPs can be used for up to six adsorption/desorption cycles. In addition, applying the Fe3O4/CS NPs on real water samples revealed that Fe3O4/CS NPs could remove TMP and SMX in the 91.23-95.95% range with RSD (n = 3) < 4. Overall, the Fe3O4/CS NPs exhibit great potential for removing TMP and SMX antibiotics from real water samples.

Effective Removal of Dyes from Wastewater by Osmanthus Fragrans Biomass Charcoal

The exploration of low-cost, high-performance adsorbents is a popular research issue. In this work, a straightforward method that combined hydrothermal with tube firing was used to produce Osmanthus fragrans biomass charcoal (OBC) from low-cost osmanthus for dye adsorption in water. The study examined the parameters of starting concentration, pH, and duration, which impacted the process of adsorption of different dyes by OBC. The analysis showed that the adsorption capacities of OBC for six dyes: malachite green (MG, C0 = 800 mg/L, pH = 7), Congo red (CR, C0 = 1000 mg/L, pH = 8), rhodamine B (RhB, C0 = 500 mg/L, pH = 6), methyl orange (MO, C0 = 1000 mg/L, pH = 7), methylene blue (MB, C0 = 700 mg/L, pH = 8), and crystalline violet (CV, C0 = 500 mg/L, pH = 7) were 6501.09, 2870.30, 554.93, 6277.72, 626.50, and 3539.34 mg/g, respectively. The pseudo-second-order model and the Langmuir isotherm model were compatible with the experimental findings, which suggested the dominance of ion exchange and chemisorption. The materials were characterized by using XRD, SEM, FTIR, BET, and XPS, and the results showed that OBC had an outstanding specific surface area (2063 m2·g-1), with potential adsorption mechanisms that included electrostatic mechanisms, hydrogen bonding, and π-π adsorption. The fact that the adsorption capacity did not drastically decrease after five cycles of adsorption and desorption suggests that OBC has the potential to be a dye adsorbent.

Bioinspired Synthesis of Silver Nanoparticles for the Remediation of Toxic Pollutants and Enhanced Antibacterial Activity

This research presents a novel and environmentally friendly approach for the synthesis of multifunctional nanobiocomposites for the efficient removal of toxic heavy metal and dye, as well as the disinfection of wastewater microorganisms. The nanobiocomposites (KAC-CS-AgNPs) were prepared by incorporating photochemically generated silver nanoparticles (AgNPs) within a chitosan (CS)-modified, high-surface-area activated carbon derived from kenaf (KAC), using a unique self-activation method. The even distribution of AgNPs was visible in the scanning electron microscopy images and a Fourier transform infra red study demonstrated major absorption peaks. The experimental results revealed that KA-CS-AgNPs exhibited exceptional adsorption efficiency for copper (Cu²⁺), lead (Pb²⁺), and Congo Red dye (CR), and showed potent antibacterial activity against Staphylococcus aureus and Escherichia coli. The maximum adsorption capacity (mg g^-1) of KAC-CS-AgNPs was 71.5 for Cu²⁺, 72.3 for Pb²⁺, and 75.9 for CR, and the adsorption phenomena followed on the Freundlich and Langmuir isotherm models and the second-order kinetic model (R² > 0.99). KAC-CS-AgNPs also exhibited excellent reusability of up to four consecutive cycles with minor losses in adsorption ability. The thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic in nature. The bacterial inactivation tests demonstrated that KAC-CS-AgNPs had a strong bactericidal effect on both E. coli and S. aureus, with MIC calculated for E. coli and S. aureus as 32 µg mL^-1 and 44 µg mL^-1, respectively. The synthesized bioinspired nanocomposite KAC-CS-AgNPs could be an innovative solution for effective and sustainable wastewater treatment and has great potential for commercial applications.

Cyclic desorption based efficacy of polyvinyl alcohol-chitosan variant resins for multi heavy-metal removal

The simultaneous removal of Cu, Pb and Fe from water bodies has been targeted in this work with polyvinyl alcohol (PVA) and chitosan (low, medium, and high molecular weight) derivative and with cyclic desorption efficacy target. For a varied range of adsorbent loading (0.2-2 g L^-1), initial concentration (187.7-563.1 mg L^-1 for Cu, 5.2-15.6 mg L^-1 for Pb, and 61.85-185.55 mg L^-1 for Fe), and resin contact time (5 to 720 min), batch adsorption-desorption studies were conducted. After first adsorption-desorption cycle, the optimum absorption capacity was 6.85 mg g^-1 for Pb, 243.90 mg g^-1 for Cu, and 87.72 mg g^-1 for Fe for the high molecular weight chitosan grafted polyvinyl alcohol resin (HCSPVA). The alternate kinetic and equilibrium models were analyzed along with the interaction mechanism between metal ions and functional groups. The cyclic desorption studies were carried out with simple eluent systems such as HCl, HNO₃, H₂SO₄, KOH, and NaOH. The experiments revealed that the HCSPVA derivative has been an impressive, reusable, and effective sorbent for the mitigation of Pb, Fe, and Cu in complex wastewater systems. This is due to its easy synthesis, excellent adsorption capacity, quick sorption rate, and remarkable regeneration capabilities.

Simple synthesis of chitosan/alginate/graphene oxide/UiO-67 amphoteric aerogels: Characterization, adsorption mechanism and application for removal of cationic and anionic dyes from complex dye media

A chitosan/alginate/graphene oxide/UiO-67 (CS/SA/GO/UiO-67) amphoteric aerogel was synthesized successfully. A series of characterization experiments of CS/SA/GO/UiO-67 amphoteric aerogel was performed by SEM, EDS, FT-IR, TGA, XRD, BET, and zeta potential. The competitive adsorption properties of different adsorbents for complex dyes wastewater (MB and CR) at room temperature (298 K) were compared. Langmuir isotherm model predicted that the maximum adsorption quantity of CS/SA/GO/UiO-67 for CR and MB was 1091.61 and 1313.95 mg/g, respectively. The optimum pH values of CS/SA/GO/UiO-67 for the adsorption of CR and MB were 5 and 10, respectively. The kinetic analysis showed that the adsorption of MB and CR on CS/SA/GO/UiO-67 was more suitable for the pseudo-second-order and pseudo-first-order kinetic model, respectively. The isotherm study revealed that the adsorption of MB and CR was consistent with the Langmuir isotherm model. The thermodynamic study demonstrated that the adsorption process of MB and CR was exothermic and spontaneous. FT-IR analysis and zeta potential characterization experiments revealed that the adsorption mechanism of MB and CR on CS/SA/GO/UiO-67 depended on π-π bond, hydrogen bond, and electrostatic attraction. Repeatable experiments showed that the removal rates of MB and CR of CS/SA/GO/UiO-67 after six cycles of adsorption were 67.19 and 60.82 %, respectively.

Chitosan-based composite films to remove cationic and anionic dyes simultaneously from aqueous solutions: Modeling and optimization using RSM

Regarding the existence of cationic and anionic dyes in the water environment developing new and effective techniques to remove them simultaneously is essential. Herein, a chitosan/poly-2-aminothiazole composite film reinforced with multi-walled carbon nanotube-Mg Al-layered double hydroxide (CPML) was created, characterized, and used as an effective adsorbent for methylene blue (MB) and methyl orange (MO) dyes removal from the aquatic medium. The SEM, TGA, FTIR, XRD, and BET methods were used to characterize the synthesized CPML. Response surface methodology (RSM) was utilized to evaluate dye removal based on the initial concentration, dosage, and pH factors. The highest adsorption capacities were measured at 471.12 and 230.87 mg g^-1 for MB and MO, respectively. The study of different isotherm and kinetic models revealed that the adsorption of the dyes onto CPML nanocomposite (NC) was correlated with the Langmuir and pseudo-second-order kinetic model, which indicated a monolayer adsorption manner on the homogeneous surface of NCs. The reusability experiment clarified that the CPML NC could be applied multiple times. Experimental results show that the CPML NC has sufficient potential for treating cationic and anionic dye-contaminated water.