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The present study manufactured and utilized the chitosan-coated fumed silica composite (CS@silica) for simultaneous adsorption of rare earth elements (REEs) of Ce(III), La(III), and Nd(III) cations in an aqueous solution. The CS@silica composite underwent characterization using a CHNOS analyzer, Brunauer-Emmett-Teller (BET) surface area analyzer, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectrophotometer, scanning electron microscope coupled with energy-dispersive X-ray (SEM-EDX) spectrophotometer, and X-ray diffraction (XRD) analyzer. The findings indicated that the CS@silica composite exhibited a lack of pores and possessed a specific surface area of 1.27 m2/g. Additionally, it was observed that the composite contained a significant amount of oxygen and nitrogen atoms, which serve as the active sites for the adsorption of REEs. The maximum adsorption capacities of Ce(III), La(III), and Nd(III) cations were determined under optimal experimental conditions. These parameters included a pH of 4, an adsorbent dose of 0.01 g, and an equilibrium duration of 20 min. The maximum adsorption capacities for Ce(III), La(III), and Nd(III) cations were found to be 341, 241, and 299 mg/g, respectively. The adsorption kinetics followed the pseudo-second-order kinetic model. The desorption percentage of REEs-loaded CS@silica composite was significantly low when exposed to deionized water and hydrochloric acid (0.01 and 0.02 M). This suggests that there is a chemical interaction between the REEs and the active site on the surface of the composite. The predominant adsorption process proposed was complexation, with ion exchange and electrostatic contact playing a minor role. The CS@silica composite is highly promising for the recovery of REEs because of its rapid adsorption and high adsorption capacities. [ABSTRACT FROM AUTHOR]

Malachite green (MG), commonly employed in the textile and dyeing sectors, is a prevalent and enduring contaminant found in wastewater and the environment. Its presence poses harmful effects to humans and aquatic organisms. This work utilised hydrogen peroxide-treated desiccated coconut waste (HPDCW) to remove MG from an aqueous solution. The HPDCW underwent characterisation utilising FTIR, SEM-EDX, pHslurry, and pHpzc. Based on the results obtained, it was found that HPDCW recorded a biosorption capacity of 211.88 mg/g, attained at a temperature of 302 K, a pH of 9, a contact period of 5 min, and a dosage of 0.02 g. MG biosorption rates accurately followed the pseudo-second-order kinetic model, while the equilibrium data presented a step-shaped isotherm model. The relatively small percentages of MG desorption observed when using distilled water and HCl (0.01 and 0.02 M) indicate that electrostatic interaction is one of the mechanisms responsible for the interaction between MG and HPDCW. There is also a possibility of the involvement of hydrogen bonding and p-p interactions. [ABSTRACT FROM AUTHOR]

Dyeing operations in industries like textiles, paper, and leather are significant contributors to environmental pollution due to the release of harmful dyes. The current study aimed to examine the use of oil palm trunk (OPT) treated with phosphoric acid (PAOPT) to remove malachite green (MG) dye from aqueous solutions through batch adsorption experiments. Spectroscopic and quantitative tests were used to characterise the PAOPT adsorbent. The effects of initial solution pH (3-6), PAOPT dosage (0.02-0.10 g), and adsorption duration (0-120 min) were studied. The adsorption rate of MG followed a pseudo-second-order kinetic model with a high regression correlation (R2) and a low chi-squared value (χ²). The single-layer adsorption of PAOPT for MG was determined to be 217.23 mg/g at a pH of 6, 0.02 g PAOPT mass, 20 min contact time, and 298 K. The percentage of MG desorption from the loaded PAOPT using distilled water and 0.01 M HCl was 0% and 19.65%, respectively, indicating the possible involvement of electrostatic interactions between the dye and PAOPT, π-π interaction and hydrogen bonding. The experimental results of the current study and the assessment with other stated adsorbents indicate that PAOPT could be used as a cost-effective alternative adsorbent for MG removal. [ABSTRACT FROM AUTHOR]

Aloe vera leaves (AVL), a by-product of agricultural waste, have been applied as a biosorbent for reducing Ni(II) ions in aqueous solutions. The biosorption capability of AVL powder was enhanced through chemical treatment with 0.10 M citric acid solution. Fourier-transform infrared (FTIR) spectrophotometer, scanning electron microscope coupled with energy dispersive X-ray (SEM-EDX), pH of point-zero-charge (pHPZC), and pHslurry analyses were used to study the surface, and chemical properties of citric acid-treated Aloe vera leaf powder (CAAVLP). The setting for experiments such as pH solution, CAAVLP dose, initial concentration, and biosorption time was investigated. Maximum Ni(II) ion biosorption capability was determined to be 48.65 mg/g based on the Langmuir model at pH 6, a CAAVLP dose of 0.02 g, initial Ni(II) concentrations of 5 to 50 mg/L and biosorption time of 120 min. The data for the isotherm and kinetics were well matched with the Freundlich and pseudo-second-order models, respectively, with high regression correlation (R²) and low chi-square (X²) values. The presence of more -COOH groups after treating AVL with citric acid resulted in more Ni(II) ions being able to be removed. [ABSTRACT FROM AUTHOR]