Utilization of Calcium Alginate Silica Based on Coral Skeleton and Wedi Awu Beach Sand as NaCl Adsorbent

Synthesis of calcium alginate silica gel based on coral skeleton and wedi awu beach sand has the potential to be used as a product to reduce NaCl levels in seawater. This research aims to maximize the potential of natural materials. The materials used in the manufacture of adsorbents are calcium from coral skeletons used as a constituent of CaCl2, silica extracted from Wedi Awu beach sand, and sodium alginate. The three materials were synthesized into a cross-linked calcium alginate silica gel. Silica extracted from beach sand was mixed with sodium alginate, and then the mixture was dripped into CaCl2 solution. The results obtained are white round-shaped adsorbent gel, which occurs because SiO2 reacts with-O-groups on sodium alginate to form a white mixture, and Ca2+ in CaCl2 will crosslink with sodium alginate when dripped, forming an adsorbent gel. In the FTIR analysis of silica calcium alginate adsorbent gel, there are-OH, C=O, C-O groups that can play an active role in NaCl adsorption. Calcium alginate silica adsorbent gel can produce the highest percent adsorption at a CaCl2 concentration of 0.5 M, with an optimum contact time of 60 minutes, namely for Na + obtained a percent adsorption of 95.24% and on Cl-of 99.19%. The results of concentration and time optimization were then tested with real seawater with a percent adsorption of Na + of 69.33% while on Cl-of 37.26%.