Synthesis and Characterization of Modified Chrysophyllum albidum Seed Sodium Alginate Copolymers for Methylene Blue Removal

Abstract

This study aimed to evaluate the methylene blue adsorption performance of sodium alginate-based copolymers synthesized from acid-treated and base-treated Chrysophyllum albidum seed. The copolymers were prepared through chemical pretreatment and copolymerization with sodium alginate, then characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy to assess functional groups, structural arrangement, and surface morphology. Batch adsorption experiments were conducted under varying pH, adsorbent dosage, temperature, and contact time, while the data were evaluated using Box Behnken optimization, Langmuir and Freundlich isotherm models, and pseudo-first-order and pseudo-second-order kinetic models. The base-treated copolymer showed superior adsorption performance, achieving 90.1% maximum methylene blue removal compared with 79.9% for the acid-treated copolymer. It also recorded higher Langmuir adsorption capacity, stronger adsorption intensity, and better surface accessibility. The optimum conditions were pH 10.45, dosage 0.58 g, temperature 36.77 °C, and contact time 174.47 min, with desirability of 1.000. The adsorption kinetics followed the pseudo-second order model. The results indicate that base-treated Chrysophyllum albidum seed sodium alginate copolymer is a promising low-cost adsorbent for methylene blue removal from wastewater.