Rapid biosorption of methylene blue by in situ cellulose-grafted poly 4-hydroxybenzoic acid magnetic nanohybrid: multivariate optimization and isotherm study

Recent Developments in the Application of Bio-Waste-Derived Adsorbents for the Removal of Methylene Blue from Wastewater: A Review

Over the last few years, various industries have released wastewater containing high concentrations of dyes straight into the ecological system, which has become a major environmental problem (i.e., soil, groundwater, surface water pollution, etc.). The rapid growth of textile industries has created an alarming situation in which further deterioration to the environment has been caused due to substances being left in treated wastewater, including dyes. The application of activated carbon has recently been demonstrated to be a highly efficient technology in terms of removing methylene blue (MB) from wastewater. Agricultural waste, as well as animal-based and wood products, are excellent sources of bio-waste for MB remediation since they are extremely efficient, have high sorption capacities, and are renewable sources. Despite the fact that commercial activated carbon is a favored adsorbent for dye elimination, its extensive application is restricted because of its comparatively high cost, which has prompted researchers to investigate alternative sources of adsorbents that are non-conventional and more economical. The goal of this review article was to critically evaluate the accessible information on the characteristics of bio-waste-derived adsorbents for MB’s removal, as well as related parameters influencing the performance of this process. The review also highlighted the processing methods developed in previous studies. Regeneration processes, economic challenges, and the valorization of post-sorption materials were also discussed. This review is beneficial in terms of understanding recent advances in the status of biowaste-derived adsorbents, highlighting the accelerating need for the development of low-cost adsorbents and functioning as a precursor for large-scale system optimization.

Effective adsorption of methylene blue dye from water solution using renewable natural hydrogel bionanocomposite based on tragacanth gum: Linear-nonlinear calculations

Today, hydrogels opened new windows to the high-tech due to their amazing features. Thus, we applied hydrogel nanocomposite (HNC) made of tragacanth gum (a kind of polysaccharide) and CaCO₃ nanoparticles to remove methylene blue dye (MBD) from the water solution. We used nonlinear and linear isotherms and kinetics as well as thermodynamics to uncover the adsorption mechanism. The results showed that the hydrogel could remove 80% of MBD. Besides, the linear form of the pseudo-second-order kinetic model fits well with the results, showing chemical interactions. We found that this process follows both Sips and Redlich-Peterson models by applying nonlinear and linear isotherm models. The maximum adsorption capacities from nonlinear and linear Sips were 1401 and 2145 mg/g, respectively. Based on the thermodynamic equations, the adsorption of MBD onto HNC was physiochemical and exothermic. According to the phenomenological calculations, diffusion from the bulk (or film diffusion, D_f = 1.2 × 10^-8 cm²/s) is the primary mechanism.

Surface molecular imprinting on polystyrene resin for selective adsorption of 4-hydroxybenzoic acid

Using chloromethylated polystyrene resin, N,N-diethylaminoethyl methacrylate, and ethylene glycol dimethacrylate as support, functional monomer and cross-linker, respectively, the molecularly imprinted resin (MIR) and non-imprinted resin (NIR) were fabricated by the combination of atom transfer radical polymerization and surface imprinting technique for the selective adsorption of 4-hydroxybenzoic acid (4-HB) from aqueous solutions. The prepared adsorbents were characterized by N₂ adsorption/desorption isotherms, Fourier-transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The adsorption processes of the 4-HB with MIR and NIR followed pseudo-second-order kinetics, and the adsorption isotherms were appreciably described by the Langmuir model. Furthermore, the adsorption efficiencies of MIR and NIR for different compounds in single and binary solutions proved that MIR exhibited high adsorption capacity and favorable selectivity toward 4-HB over other structurally related organic compounds (i.e., benzoic acid, 2-hydroxybenzoic acid, 3-hydroxybenzoic acid, phenol, and 2-hydroxynaphthalene). In addition, MIR could effectively remove 4-HB from a simulated effluent in a dynamic adsorption experiment. This study illustrates in-depth perspectives on the adsorption mechanisms of 4-HB onto MIR; interactions between the adsorbate and adsorbent were proposed based on the adsorption behaviours and instrumental analyses. The resulting MIR is a promising material for the interference-free adsorbent in the selective adsorption of 4-HB from mixed solutions.