Fabrication of a novel alginate-xanthan biopolymer hydrogel bead for cationic surfactant removal from aqueous medium

Cationic surfactant (CS) is one of the alarming emerging contaminants often found in municipal and industrial wastewater. Various research articles have already reported about the toxicity of CS. In the current research work, sustainable and green alginate (Ag) and alginate composite beads with xanthan gum (AgX) are explored for the adsorptive elimination of model CS, cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB), from wastewater. The composite (AgX) beads showed relatively better performance than Ag beads in terms of mechanical strength and equilibrium time. Studies on FTIR spectra, SEM analysis, size distribution, pH(zpc) measurement, and elemental analyses were conducted in order to characterize the adsorbent and to get an insight into the adsorption phenomenon. At the end of 8 days' equilibrium time, the maximum adsorptive retention capacity of the AgX beads was obtained as similar to 310 mg/g with an initial CPC concentration of 600 mg/L, using an adsorbent dose of 1.5 g/L. A layered isotherm with varying slopes was obtained, indicating different stages of CPC adsorption. CPC uptake by hydrogel beads was associated with significant shrinkage of the beads. Removal of CPC from real wastewater was possible with good efficiency. The effect of pH and interfering ions on CPC removal was examined. The results showed that the pH range of 5.5-6 was the optimum, and there was no interference from Co(II), Ni(II), and Mg(II) ions. The results showed good reproducibility with a relative standard deviation (RSD) < +/- 10%.