Polymer-based nanocomposites reinforced with functionalized-MWCNT and their utilizing as sorbent for removal of MB and Cd2+ ion from water media: A review

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.

Recent advances in chitosan-based nanocomposites for adsorption and removal of heavy metal ions

Due to the high concentration of various toxic and dangerous pollutants, industrial effluents have imposed increasing threats. Among the various processes for wastewater treatment, adsorption is widely used due to its simplicity, good treatment efficiency, availability of a wide range of adsorbents, and cost-effectiveness. Chitosan (CS) has received great attention as a pollutant adsorbent due to its low cost and many -OH and -NH2 functional groups that can bind heavy metal ions. However, weaknesses such as sensitivity to pH, low thermal stability and low mechanical strength, limit the application of CS in wastewater treatment. The modification of these functional groups can improve its performance via cross-linking and grafting agents. The porosity and specific surface area of CS in powder form are not ideal, so physical modification of CS via integration with other materials (e.g., metal oxide, zeolite, clay, etc.) leads to the creation of composite materials with improved absorption performance. This review provides reports on the application of CS and its nanocomposites (NCs) for the removal of various heavy metal ions. Synthesis strategy, adsorption mechanism and influencing factors on sorbents for heavy metals are discussed in detail.

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.

Design strategies, surface functionalization, and environmental remediation potentialities of polymer-functionalized nanocomposites

Inorganic nanoparticles (NPs) have a tunable shape, size, surface morphology, and unique physical properties like catalytic, magnetic, electronic, and optical capabilities. Unlike inorganic nanomaterials, organic polymers exhibit excellent stability, biocompatibility, and processability with a tailored response to external stimuli, including pH, heat, light, and degradation properties. Nano-sized assemblies derived from inorganic and polymeric NPs are combined in a functionalized composite form to import high strength and synergistically promising features not reflected in their part as a single constituent. These new properties of polymer/inorganic functionalized materials have led to emerging applications in a variety of fields, such as environmental remediation, drug delivery, and imaging. This review spotlights recent advances in the design and construction of polymer/inorganic functionalized materials with improved attributes compared to single inorganic and polymeric materials for environmental sustainability. Following an introduction, a comprehensive review of the design and potential applications of polymer/inorganic materials for removing organic pollutants and heavy metals from wastewater is presented. We have offered valuable suggestions for piloting, and scaling-up polymer functionalized nanomaterials using simple concepts. This review is wrapped up with a discussion of perspectives on future research in the field.

Construction of CdS-Tetrahymena thermophila hybrid system by efficient cadmium adsorption for dye removal under light irradiation

The water pollution caused by heavy metals and dyes emitted by industries has become a worldwide problem. These pollutants are difficult to be biodegraded. Even at low concentrations, they are toxic and at last threaten human health. Herein, while using Tetrahymena thermophila, a single-celled ciliate protozoa, to enrich and remove the heavy metal Cd²⁺ from water, CdS nanoparticle-Tetrahymena thermophila hybrid system (CdS-T. thermophila) for dye pollution remediation under light irradiation was developed. The conditions of Cd²⁺ enrichment and removal by T. thermophila, construction of efficient CdS-T. thermophila, and decolorization of Congo red using CdS-T. thermophila were investigated. In the presence of cysteine ethyl ester, the removal rate of Cd²⁺ by T. thermophila was 94% at low Cd²⁺ concentration of 1 mg L^-1. The adsorption capacity of T. thermophila to Cd²⁺ reached 43 mg g^-1 at Cd²⁺ concentration of 80 mg L^-1. Using 0.1 g L^-1 constructed CdS-T. thermophila, the decolorization rate of 50 mg L^-1 Congo red solution reached 95% in 60 min under light irradiation. This study provides a new insight to effective removing Cd²⁺ from water by T. thermophila to construct the CdS-T. thermophila and using it to remediate dye pollution in the environment.