Serpentine as adsorbent for removal of phosphate from water

Abstract

Adsorption of phosphate onto chrysotile, non-asbestiform serpentine, olivine and alumina increases with increasing phosphate concentration, solid concentration, and with decreasing pH (except some cases at extremely high or low pH values). Under some experimental conditions, the phosphate adsorption capacities of chrysotile, olivine, serpentine (N.Y.), serpentine (Cal.) and alumina can be as high as 10, 8.6, 4.6, 3.4, 0.7 mg PO 3-4/g solid, respectively. Chrysotile was also capable of removing NH+4 from water. Removal of some of the phosphate by chrysotile can be achieved by the formation of (text indistinguishable) as a precipitate when both phosphate and ammonia are present in solution. The pH appears to be an important factor controlling the minerals’ surface charge, thus affecting phosphate adsorption into the minerals. The phosphate adsorption mechanism may involve anion exchange with the replacement of OH- in the minerals’ surface and chemical reaction in addition to electrostatic attraction of phosphate for the minerals’ surface.