Green coagulation and flocculation: Scenedesmus algal extract-loaded chitosan/poly(vinyl alcohol) cryogel for effective water treatment

This study presents an eco-friendly approach to treat contaminated and turbid water through the development of cryogels loaded with bioactive compounds derived from Scenedesmus algal extract (ScAE) based on chitosan/poly(vinyl alcohol) (Cs/PVA) matrix. Scenedesmus sp., a green microalga known for its bioactive properties, was cultivated and processed to obtain extracts with coagulation potential. This extract was incorporated into cryogel at concentrations of 2, 4, 6, and 8 mL to improve coagulation and flocculation processes. Physicochemical analyses, including Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM), confirmed the successful synthesis and structural integrity of ScAE-loaded cryogels, demonstrating uniform morphology, high porosity, and enhanced mechanical strength with increasing ScAE concentration. Significant results highlight the effectiveness of a 50 mg ScAE-loaded cryogel, which achieved significant reductions in turbidity, from 6 NTU to 1.6 NTU, and total suspended solids (TSS), from 16 mg/L to 6 mg/L, in water samples. The highest concentration cryogel (ScAE-8) also demonstrated a 62 % reduction in nitrate levels, underscoring its capability for broader contaminant removal. These results reveal that the ScAE-loaded cryogels not only provide an effective, biodegradable alternative to conventional chemical coagulants such as alum but also align with green chemistry approaches, potentially providing a sustainable solution for the large-scale water treatment facilities while lowering the negative environmental consequnces.