Agricultural waste to environmental purifier: Application and mechanism of aminated pomelo peel for adsorption of anionic dyes and Cr(VI)

Abstract

This study investigated the transformation of an agricultural byproduct, pomelo peel, into an environmental purifier by crosslinking assisted surface amination process and its use in wastewater treatment application. Surface morphology and textural analysis showed that the functionalized surface-amidated pomelo peel (SA-PP) attained a lamellar structure with an average pore size of 6.52 nm and a specific surface area of 7.82 m² g−1. Zeta potential measurements confirmed that SA-PP exhibits a positive surface charge within a pH range of 3–11. This surface characteristic facilitated the effective adsorption of anionic dyes by SA-PP, including amaranth red (Qe = 497.15 mg g−1), methyl orange (Qe = 247.93 mg g−1), bright blue (Qe = 231.53 mg g−1), and lemon yellow (Qe = 116.77 mg g−1), as well as heavy metal ions like hexavalent chromium (Cr(VI),Qe = 193.17 mg g−1). Further investigations on the adsorption of amaranth red and Cr(VI) indicated that SA-PP achieved equilibrium after 30 min. The process followed the pseudo-second-order and Langmuir isotherm models, indicating monolayer adsorption. The adsorption efficacy of SA-PP remained consistent across a wide range of pH levels. After five cycles, SA-PP was able to retain more than 60 % of its adsorption capacity, highlighting its potential as a sustainable, cost-effective, non-toxic, and biodegradable adsorbent for wastewater treatment applications.