Remediation of phenol and p-nitrophenol from contaminated water using raw and quaternized Annona muricata L. peels

The aim of this research was to evaluate the effectiveness of modified fruit peels as sustainable adsorbents for removing phenol and p-Nitrophenol (PNP) from aqueous solutions. Fruit peels from Annona muricata L, (graviola peels) were chemically modified by anchoring functional groups such as NH4+, C-N, CH3, and C-H to enhance adsorption capacity. The concentrations of phenol and PNP were determined using UV-Vis spectrometry at 270 nm and 318 nm, respectively. Optimization studies identified pH 4 as optimal for maximum removal efficiency. Results showed that adsorption decreased with increasing contaminant concentrations but increased with higher adsorbent dosages. The adsorption data conformed well to the Langmuir isotherm and obeyed second-order kinetics, indicating monolayer chemisorption. The highest adsorption capacities were 54.95 mg/g for phenol (QGP) and 106.38 mg/g for PNP (QAP). Thermodynamic parameters confirmed that the adsorption process was exothermic, spontaneous, and random. Both raw and quaternized adsorbents could be regenerated with 0.5 M HCl after a single cycle, highlighting their potential for cost-effective and sustainable water treatment. This study demonstrates that locally available fruit peels, in raw and modified forms, can serve as efficient, eco-friendly adsorbents for removing hazardous phenolic compounds from contaminated water, contributing to environmental protection and public health.