However, maximum phosphate was removed in initial 120 min. For example, after 15, 45 and 120 min of adsorption, the removal percentage of phosphate by mussel shells was 29.56%, 41.62% and 66.59%, respectively, of that at 720 min.
Previous studies suggested that P immobilization on calcite was attributed to (i) binding of phosphate and calcium resulting in precipitation of calcium phosphate, and (ii) adsorption of phosphate on the surface of adsorbent.