Biofilm hydrogel derived from physical crosslinking (self-assembly) of xanthan gum and chitosan for removing Cd2+, Ni2+, and Cu2+ from aqueous solution.

This study aimed to fabricate a series of biodegradable hydrogel films by gelating/physically crosslinking a blend of xanthan gum (XG) and chitosan (CS) in various combinations using a facile, green, and low cost solution casting technique. The adsorption of Cd2+, Cu2+ and Ni2+ by the XG/CS biofilm in aqueous solution was studied in batch experiments to determine how the pH of the solution, contact time, dosage of adsorbent, initial metal ion concentration and ionic strength affect its adsorption. A highly pH-dependent adsorption process was observed for three metal ions. A maximum amount of Cd2+, Ni2+, and Cu2+ ions was adsorbable with 50 mg of the adsorbent at pH 6.0 for an initial metal concentration of 50 mg.L-1. An empirical pseudo-second-order model seems to fit the kinetic experimental data reasonably well. It was found that the Langmuir model correlated better with equilibrium isotherm when compared with the Freundlich model. For Cd2+, Ni2+, and Cu2+ ions at 25 °C, the maximum monolayer adsorption capacity was 152.33, 144.79, and 139.71 mg.g-1, respectively. Furthermore, the biofilm was capable of regenerating, allowing metal ions to adsorb and desorb for five consecutive cycles. Therefore, the developed biodegradable film offers the potential for remediation of specified metal ions.

A self-assembling hydrogel nanocomposite based on xanthan gum modified with SiO2 NPs and HPAM for improved adsorption of crystal violet cationic dye from aqueous solution.

This paper presents the rational design and novel synthesis of multifunctional nanocomposite hydrogel derived from xanthan gum (XG) modified with silica nanoparticles and partially hydrolyzed polyacrylamide (HPAM) via H-bonding interactions (self-assembly) through the "green" gelation process in water. Different techniques have been employed to characterize HPAM/SiO2@XG, including FT-IR, FE-SEM, XRD, TEM, BET, and TG/DTG as well as swelling kinetics. Crystal violet (CV)'s adsorption performance was investigated using batch experiments by varying various variables involving adsorbent composition, pH, adsorbent quantity, contact time, CV concentration, ionic strength, and temperature. A well-fitting Langmuir isotherm was found for the adsorption data at 30 °C and pH 7.0, yielding 342.19 mg CV/g as the equilibrium state's maximum adsorption (qm). CV adsorption data agreed better with the pseudo-second-order model than other kinetic models. Furthermore, the HPAM/SiO2@XG nanocomposite hydrogel showed a significant increase in adsorption capacity over the SiO2@XG hydrogel precursor. According to thermodynamic analysis, CV adsorbs to HPAM/XG@SiO2 spontaneously and exothermically. Our results showed that the nanocomposite hydrogel's functional groups interact with CV predominantly through electrostatic interactions, coupled with H-bonding. Nanocomposite hydrogel has been regenerated using a five-cycle adsorption-desorption process, and the efficiency of CV removal has remained a satisfactory level of removal efficiency (94.5 % to 71.5 %).

Chitosan and silica nanoparticles-modified xanthan gum-derived bio-nanocomposite hydrogel film for efficient uptake of methyl orange acidic dye.

In this contribution, a bio-nanocomposite hydrogel film (CS/XG.SiO2) of chitosan/silica NPs-modified xanthan gum was prepared via a facile solution casting blending approach and utilized to capture the anionic methyl orange (MO) from aqueous solution. A Taguchi standard method was used to optimize the hydrogel nanocomposite synthesis reaction conditions after comprehensive characterization using various techniques. Under various operating parameters, the hydrogel biofilm was tested for its effectiveness in adsorbing MO dye in a batch process. In agreement with Langmuir isotherm, the CS/XG.SiO2 biofilm was capable of adsorbing MO at a maximum capacity of 294 mg/g at pH 5.30, contact time 45 min, temperature 25 °C, and concentration (C0) 50 mg/L. Pseudo-second-order model and adsorption kinetics data well matched. The thermodynamic data indicate that adsorption occurred spontaneously and exothermically. The main mechanisms driving the adsorption are electrostatic interactions and hydrogen bonding between the CS/XG.SiO2 nanocomposite and the dye. Furthermore, the biofilm is regenerative, allowing for up to five reuses while maintaining a 75 % dye removal efficiency. This study highlights that the CS/XG.SiO2 hydrogel nanocomposite is an inexpensive, reusable, and eco-friendly bio-adsorbent that is capable of anionic dye adsorption.

Preparation of chitosan-based ternary nanocomposite hydrogel film by loading graphene oxide nanosheets as adsorbent for enhanced methylene blue dye removal.

Our objective in this study is to fabricate a novel chitosan-based ternary nanocomposite hydrogel film by incorporating graphene oxide (GO) nanosheets into a chitosan/partially hydrolyzed polyacrylamide (PHPA) network to boost adsorption efficiency through one step self-assembly process in water. Basically, H-bonding interactions drive the formation of a crosslinking network structure. The Batch adsorption experiments evaluated the hydrogel nanocomposite's MB adsorption performance. By loading GO, surface roughness, swelling percentage (from 21,200 % to 35,800 %), elastic modulus of up to 73.7 Pa, and adsorption characteristics (from 282 mg/g to 468 mg/g) were enhanced. The nanocomposite displayed outstanding thermally/pH responsiveness properties. MB adsorption equilibrium was reached after 45 min and the adsorption capacity was 476.19 mg.g-1 when the initial concentration was 100 mg/L. The MB adsorption kinetics and isotherms by the nanocomposite were well correlated by the PSO and the Langmuir models (R2 > 0.99), respectively. The loaded nanocomposite was shown to be regenerative for five cycles through desorption studies. Thermodynamic analysis indicated that MB adsorption occurred spontaneously (ΔG°: -16.47 kJ/mol, 303 K) and exothermically (ΔH°: -79.49 kJ/mol). A plausible adsorption mechanism was proposed for the nanocomposite developed for MB removal. Our results can contribute to the design and fabrication of nanocomposite adsorbents to treat wastewater.

An all-biopolymer self-assembling hydrogel film consisting of chitosan and carboxymethyl guar gum: A novel bio-based composite adsorbent for Cu2+ adsorption from aqueous solution.

A novel bio-based composite adsorbent, all biopolymer self-assembled hydrogel film has been prepared by eco-friendly amalgamating chitosan (CS) and carboxymethyl guar gum (CMGG) biopolymers in water without needing small molecules for cross-linking. Various analysis demonstrated the electrostatic interactions and hydrogen bondings within the network structure are responsible for gelling, crosslinking, and forming a 3D structure. Various experimental parameters were optimized to evaluate the CS/CMGG's potential for removing Cu2+ ions from aqueous solution, including pH, dosage, Cu(II) initial concentration, contact time, and temperature. The pseudo-second-order kinetic and Langmuir isotherm models are highly correlated with the kinetic and equilibrium isotherm data, respectively. Using the Langmuir isotherm model for an initial metal concentration of 50 mg/L at pH 6.0 and 25 °C, the maximum adsorption of Cu(II) was calculated to be 155.51 mg/g. A combination of adsorption-complexation and ion exchange must be involved in Cu(II) adsorption on the CS/CMGG. Five cycles of the loaded CS/CMGG hydrogel regeneration and reuse were successfully achieved without an appreciable difference in Cu(II) removal percentage. Thermodynamic analysis indicated that copper adsorption occurred spontaneously (ΔG°: -2.85 J/mol, 298 K) and exothermically (ΔH°: -27.58 J/mol). A reusable bio-adsorbent for removing heavy metal ions was developed that is eco-friendly, sustainable, and efficient.

Occurrence, identification, and discharge of microplastics from effluent and sludge of the largest WWTP in Iran-South of Tehran.

Microplastic pollution is a serious threat to the biota and humans, and wastewater treatment plants act as a pathway for entering microplastics into the environment. This study discusses the identification and quantification of microplastics in the south of Tehran municipal WWTP. The sampling was repeated three times in a month, overall, nine times for water samples and once a month in total, three times for digested sludge samples by steel bucket with the WPO method. The microplastics from water and digested sludge samples were identified using the micro-Raman microscope. According to this study, 98.9% of microplastic particles in effluent and 99.2% of microplastics particles in the sludge were fibers. The influent contained an average of 180 ± 4.3 MP/L and was reduced to 5.3 ± 0.31 MP/L in the final effluent. Despite this significant reduction, we calculate that this WWTP releases 2.3 × 109 microplastics per day through final effluent and 1.61 × 1010 particles per day through dried sludge into the environment. We performed micro-Raman analyses and ICP mass to measure the amount of heavy metal absorption of MPs. In addition, SEM analyses were used to study the surface morphology of microplastic particles. PRACTITIONER POINTS: Fourteen different polymers were identified in the influent, effluent, and digested sludge. The main collected shapes obtained were fiber, film, and fragment, which fiber was the predominant polymer in this WWTP. The plant releases 2.3 * 109 MPs per day to its downstream environment. This WWTP has average removal with an efficiency of 99.06%.

A novel route for synthesis of cross-linked polystyrene copolymer beads with tunable porosity using guar and xanthan gums from bioresources as alternative synthetic suspension stabilizers.

Cross-linked polymer beads with different cross-linking agent loading were prepared by carrying out cross-linking suspension copolymerization of styrene-divinylbenzene (St- DVB) monomers using guar gum (GG) and xanthan gum (XG) from bioresources as eco-friendly suspension biopolymer stabilizers in the presence of non reactive diluents. The effects of GG and XG as suspension biostabilizers on the characteristics of the styrene copolymer beads were investigated regarding thermal properties, porosity characteristics, solvent swelling ratio, and surface morphologies using TGA, DSC, XRD, SEM, BET analyses. Spherical and regular beads with smooth surface were produced and the average particle size was in the range 170-290 µm (50-80 mesh size). The porosity characteristics of the produced beads including surface area and pore volume were in range 0.45 m2/g and 32-45 ml/g, respectively. Overall, the present article provided a novel route to prepare cross-linked polystyrene copolymer beads with tunable porosity suitable for catalyst support.