Engineered clay pellets functionalized with industrial residuals for phosphorus removal from agricultural runoff

Abstract

Naturally occurring Ca-bentonite and kaolinite clay minerals acted as low-cost adsorbents for removing phosphorus (P) from waste water and soil. We evaluated the potential of engineered clay pellets prepared with metal waste residuals (steel slag and drinking water treatment residual) and functionalized with polymeric surfactants (Triton-X 100, Tween 20, Tween 80 and carboxymethyl cellulose) on agricultural runoff treatment. Aluminum-based drinking water treatment residual (DWTR) and Ca-bentonite combination demonstrated the maximum (293 ± 39 mg kg⁻¹, 64%) P removal, followed by steel slag and Ca-bentonite (53%). Functionalization of Ca-bentonite pellets with polymeric surfactants dramatically enhanced the negative performance (−2 mg kg⁻¹) of raw Ca-bentonite to a positive P removal of 40 mg kg⁻¹. P desorption trials on functionalized pellets determined reusability and practicality of media pellets. Among all pellets, steel slag and kaolinite showed about 80% desorption of P. The protocol incorporating metal waste residuals offers low cost and pilot-scale production of media pellets for field evaluation.