The effects of chemical modification on adsorbent performance on water and wastewater treatment - A review

Investigation of synergistic effects incorporating esterified lignin and guar gum composite aerogel for sustained oil spill cleanup

The recently developed aerogel demonstrates a high capacity for pollutant absorption, making it an environmentally friendly option for oily water treatment. In an effort to reduce the adverse effects of the black liquor accumulation in the pulp industry, this study focused on utilizing the mentioned abundant bio-resource lignin, which can be applied to various high-value applications such as 3D porous materials for oil spill cleanup. Lignin, precipitated from the black liquor, was esterified using maleic anhydride as the esterifying reagent to enhance the hydrophobicity. Then, the composite aerogel fabricated from esterified lignin and guar gum (GG) was successfully prepared through the facile freeze-drying, using glutaraldehyde (GA) as the cross-linker. The resulting aerogel exhibited high porosity values exceeding 95%, low density (27.4 mg/cm3), and an impressive absorption capacity of 32.5 g/g for sunflower oil. These results demonstrate the potential of black liquor utilization as a bio-waste source of lignin and highlight the cost-effective guar gum-esterified lignin composite aerogel, which exhibits remarkable oil absorption capabilities and environmental sustainability promotion.

Acidified groundnut cake for enhanced bio adsorption of anionic textile dye Reactive Red 195

This study focuses on the improvement of bioremediation of textile dye Reactive Red 195 using agro-industrial waste, groundnut oil cake (GNOC) obtained after oil-pressing. The treatment of GNOC with 1 N H2SO4 had resulted in physiochemical changes on the insoluble porous adsorbent, which improved their adsorption efficiency. The dye removal efficiency increased from 55% to 94% on acidification of GNOC. The raw groundnut oil cake (RGNOC) and acid-treated groundnut oil cake (AGNOC) were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction, and zeta potential. The rate and efficiency of dye adsorption were examined using adsorption kinetics and isotherm models. The results confirm that acid-treated GNOC eliminates impurities, alter the surface functional groups, and significantly increase porous surface areas of RGNOC. The investigation of key factors such as contact time, initial concentration of dye, static/agitation impact, particle size, and adsorbent dose had significantly influenced adsorption capacity of GNOC. Adsorption of dye fits best into the Langmuir model and equilibrium data of dye on AGNOC was explained by psuedo-second-order reaction with maximum adsorption capacity of 12.65 mg/g. This emphasis AGNOC has a very excellent potential to remove the textile dye Reactive Red dye from industrial effluent.

Biosorbent Based on Poly(vinyl alcohol)-Tricarboxi-Cellulose Designed to Retain Organic Dyes from Aqueous Media

Methylene Blue, a cationic dye, was retained from aqueous solutions using a novel biosorbent made of poly(vinyl alcohol) reticulated with tricarboxi-cellulose produced via TEMPO oxidation (OxC25). The study of the Methylene Blue biosorption process was performed with an emphasis on operational parameters that may have an impact on it (such as biosorbent concentration, pH of the aqueous media, and temperature). The current study focused on three areas: (i) the physic-chemical characterization of the biosorbent (scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX)); (ii) biosorption data modeling to determine the quantitative characteristic parameters employing three equilibrium isotherms (Langmuir, Freundlich, and Dubinin-Radushkevich-DR); and (iii) the study of temperature influence. The results of the study showed that the Langmuir model provided a good fit for the experimental data of biosorption, realizing a maximum capacity of 806.45 mg/g at 20 °C. The free energy of biosorption (E) evaluated by the DR equation was in the range of 6.48-10.86 KJ/mol. The values of the thermodynamic parameters indicated an endothermic process because the free Gibbs energy ranged from -9.286 KJ/mol to -2.208 KJ/mol and the enthalpy was approximately -71.686 KJ/mol. The results obtained encourage and motivate the further study of this biosorption process by focusing on its kinetic aspects, establishing the biosorption's controlled steps, identifying the mechanism responsible for the retention of textile dyes presented in moderate concentration in aqueous media, and studying the biosorption process in a dynamic regime with a view to applying it to real systems.