Synthesis of hydrogels derived from microalgae polysaccharides (extracted from Spirulina platensis) for β-blocker removal from wastewaters

Introduction

Wastewater purification from widely prescribed pharmaceuticals is a critical global priority. β-blockers used to treat cardiovascular diseases are frequently detected in wastewater and have been shown to exert toxic effects on various organisms. Adsorption onto green materials has emerged as an efficient, sustainable, and environmentally friendly technique for removing such contaminants from aquatic matrices.

Methods

Μicroalgae polysaccharides (MPs) have been extracted from Spirulina platensis biomass by a hot water extraction process. Sodium carboxymethyl cellulose (CMC) has been employed as a second hydrogel building block due to its mechanical robustness and its plethora of hydroxyl groups, which serve as potential crosslinking sites via esterification with citric acid. Thin MPS:CMC:CA (21:62:17 wt:wt:wt) films have been produced by water solution casting method followed by thermal curing at 80^οC and characterized by FTIR and SEM. Batch adsorption experiments towards atenolol have been conducted.

Results

The successful synthesis of the hydrogel was confirmed. The optimum pH value was found to be 9, with a removal efficiency of 82% (C_o = 50 mg/L, dose = 1 g/L, T = 30 °C). Adsorption exhibited rapid kinetics, with 69% atenolol removal within the first 15 min and an optimum time of 150 min; the pseudo-second-order model better described the process.

Conclusions

The results indicate that microalgal polysaccharide-based hydrogels, produced in accordance with Green Chemistry Principles #3, #5, #7, and #12, can efficiently and rapidly remove a model β-blocker drug from wastewater via a chemisorption-driven adsorption mechanism.