Addition of Thiourea Host Monomer to Polymer Flocculants to Improve Selectivity of Phosphate Sorption

Inorganic phosphate is a common nutrient that is applied as a fertilizer\r\nto both agricultural fields as well as urban settings such as private yards,\r\npublic parks and other urban landscaping. While phosphate typically binds\r\ntightly to soil, movement of phosphate off of application sites can occur\r\nthrough soil erosion. The soil and its bound phosphate can then end up in\r\nsurface waters such as rivers and lakes. Phosphate found in surface water\r\nbodies exists both as bound to the suspended clay as well as that free in\r\nsolution. Elevated phosphate concentration in surface waters can lead to algal\r\nblooms and eutrophication. While the phosphate bound to clay in suspension in\r\nsurface water bodies can be removed by commercially available polymer\r\nflocculants, the phosphate that is free in solution is more challenging as it\r\nis usually found in low concentrations and other anionic salts are generally\r\npresent in higher concentrations. To remove phosphate from contaminated water\r\nsystems, where other anions exist at higher concentrations, it is favorable to\r\nhave a method of removal that is selective for phosphate. As a proof of\r\nprinciple, thiourea derivatized polymer flocculants were examined for the\r\nselective removal of phosphate in the presence of competing anions. The polymer\r\nflocculants exhibited selectivity for phosphate through hydrogen bonding and\r\nwere effective at removing up to 43% of phosphate from simulated wastewater.\r\nComputational studies and 1H NMR were used to investigate the\r\nselectivity of the thiourea monomer for phosphate over competing anions such as\r\nchloride and sulfate.