Sorption of Phosphate onto Surfactant-Modified Zeolite Particles

Slow-release phosphorous (P) fertilizer is basically considered as an approach to increase the efficiency of P fertilization on agricultural lands. This study aimed to examine the effect of pH solutions (3.5, 7, 9 and 11), contact times (10, 15, 30, 60, 90, 120 and 150 minutes), and solid-solution ratios (1:500 , 1:1000, and 1:1500) on the capability of zeolite as a material for the development of slow-release fertilizers for absorbing phosphate ions. The surface of natural zeolite was chemically modified through surfactant addition (hexadecyltrimethylammonium bromide - C9H42BrN or HDTMABr), and the capability of surfactant-modified zeolite (SMZ) to adsorb phosphate ions was studied through batch experiments. Results of the study showed that pH solution affected the sorption of phosphate ions onto SMZ, in which pH solution of 5.0 showed high P adsorption and was below the pHpzc of SMZ. The amount of adsorbed P onto SMZ does not vary based on changes in contact time. Result of the study also revealed that the maximum sorption capacity (Qmax) of phosphate ions onto SMZ increases with increasing solid-solution ratios. Results of this study show that SMZ may potentially be used as an material for the development of slow-release P fertilizers, in which the pH solution and solid-solution ratio control the amount of sorbed P onto SMZ