Microcellular Injection-Molded LDPE/Activated Carbon Composites: Material Properties and Arsenic [As(III)/As(V)] Adsorption Performance

Arsenic contamination in water bodies caused by acid mine drainage (AMD) and industrial effluents presents severe threats to public health and aquatic ecosystems. Although activated carbon (AC) is an effective adsorbent, conventional powdered AC suffers from severe operational limits, including filter clogging, high pressure drop, and secondary pollution. Encapsulating AC inside dense low-density polyethylene (LDPE) matrices resolves powder handling issues but severely restricts contaminant mass transport. In this study, novel lightweight LDPE/AC composite foams (1, 3, 6, and 10 wt% AC) were fabricated using microcellular injection molding with supercritical nitrogen (scN2). The microcellular architecture thinned the polymer cell walls and generated an interconnected porous cell network, exposing embedded AC particles directly to the aqueous media. Morphological and thermal analyses confirmed uniform filler dispersion and preserved matrix stability, with the 10 wt% AC composite foam reaching a high BET surface area of 374 m2/g. Tensile modulus increased with AC loading up to 2535 MPa. Batch adsorption studies demonstrated optimal removal efficiency for As(III) at pH 7–8 and As(V) at pH 3, achieving maximum adsorption capacities of 20.71 mg/g and 24.00 mg/g, respectively. Treated water streams successfully met the WHO and South African SANS 241:2015 drinking water standard of 10 ppb. The adsorption dynamics obeyed pseudo-second-order kinetics and fitted the Freundlich isotherm model, indicating multi-layer chemisorption across heterogeneous surfaces. Desorption using 0.1 M EDTA retained high efficiency over 10 consecutive cycles. This work demonstrates microcellular LDPE/AC composite foams as a scalable, high-strength, and durable material platform for heavy metal remediation.