Synthesized and characterization of calcium alginate beads as biosorbent of pollutants dye and phosphate from aqueous solution

In this study, we employed sodium alginate, a naturally occurring biodegradable biopolymer, to create calcium alginate beads through the cross-linking process using CaCl2 as the gelling agent. The obtained beads were subjected to characterization through various analyses, including textural and structural structure via N2 adsorption/desorption isotherm via Brunauer–Emmett–Teller method, Fourier-transform infrared spectroscopy, X-ray diffraction, and UV-Visible diffuse reflectance analyses. The effectiveness of this adsorbent was investigated in the removal of Auramine O dye (AO) and phosphate from aqueous solutions through an adsorption process. An initial examination of Auramine O and phosphate removal using calcium alginate beads as the adsorbent was conducted to identify the optimal adsorption conditions, including contact time (adsorbate/adsorbent), initial adsorbate concentration, pH, and initial adsorbent quantity. A full factorial design matrix was used to study the direct effects and interactions of the principal parameters. Experimental results show that under the optimal conditions, calcium alginate beads demonstrate significant adsorption capabilities, achieving a phosphate removal rate of 82.5% and an AO dye removal rate of 48% within a 180 min timeframe. The adsorption findings closely align with the Langmuir model in the case of Auramine O and the Freundlich model for phosphate indicating monolayer and multilayer adsorption process, respectively. Moreover, the pseudo-second-order model fits effectively for both AO and phosphate, indicating a chemisorption process.