Phenol Adsorption from Water Using Raw and Quaternized Waste Sorbents: Isotherm, Kinetic, and Thermodynamic Analysis
Year: 2026
Type: preprint
Abstract: This study evaluates the adsorption of phenol from aqueous solutions using raw and quaternized peels derived from Cucumis metuliferus Thunb . (RTP/QTP) and Aframomum melegueta (RAP/QAP), abundant agricultural wastes in Kenya's Ruiru Sub-County. Phenolic pollutants from industrial effluents and agricultural runoff pose severe risks to aquatic ecosystems and human health, including toxicity, carcinogenicity, and bioaccumulation. Traditional remediation techniques such as incineration, advanced oxidation, and membrane filtration are costly, energy-intensive, and prone to secondary pollution, limiting their feasibility in developing regions. In contrast, these zero-cost biosorbents leverage natural lignocellulosic structures, with quaternization—employing epichlorohydrin, propylene oxide, and polyDADMAC—introducing quaternary ammonium groups to boost porosity, surface charge, and affinity for anionic phenolics via enhanced electrostatic interactions and hydrogen bonding. Raw peels were processed into powders (< 1 mm), while modified versions underwent epoxy activation and amination. Batch adsorption experiments optimized critical parameters: pH 4 (maximizing protonation), contact time 30–60 min, sorbent dose 0.03–0.05 g/20 mL, initial concentrations 5–60 mg/L, and temperature 298 K. Quaternized sorbents excelled, achieving 95.95% phenol removal (QAP) and q max of 17.61 mg/g, outperforming raw counterparts by 2-4-fold. Langmuir isotherms (R² > 0.90) confirmed monolayer chemisorption, pseudo-second-order kinetics (R² > 0.89) indicated chemisorption control (K 2 up to 0.124 g/mg/min), and thermodynamics revealed exothermic (ΔH° -10 to -18 kJ/mol), spontaneous (ΔG° negative), entropy-increasing processes favoring low temperatures. Regeneration via 0.5 M HCl sustained > 50% efficiency over five cycles, with Ruiru River spiked samples showing 20–29% removal despite matrix effects. These findings affirm quaternized peels as sustainable, regenerable sorbents for phenolic wastewater treatment, promoting waste valorization and circular economy principles in resource-scarce settings.
Source: Research Square
Authors: James Ndiritu, John Wamumwe Mwangi
Institutions: Turkana University College, Novosibirsk State University
Language: English
Subfield: Water Science and Technology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204760841