Organic reagents for removing heavy metals from a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and wet-process phosphoric acid

Abstract

Fertilizer solutions and wet-process phosphoric acid (WPA) contain heavy metal impurities such as cadmium, zinc, lead, copper, manganese, and chromium. Trisodium trithiocyanuric acid (TMT-15), sodium trithiocarbonate (5% Na2CS3), and sodium polythiocarbonate (Thio-Red II) were evaluated as precipitating agents for heavy metals in a 10-34-0 (N-P2O5-K2O) grade fertilizer solution and WPA. A water-insoluble starch xanthate was also evaluated as an adsorbent for the heavy metals in 10-34-0 (N-P2O5-K2O) and WPA. Arsenic (24−99+%), cadmium (36−97+%), copper (98+%), mercury (96+%), lead (83−88+%), and zinc (8−83+%) precipitated from 10-34-0 (N-P2O5-K2O) upon the addition of each organic reagent, while levels of manganese and chromium were unaffected. Mercury (97+%), lead (75+%), cadmium (11−38%), copper (99+%), and chromium (3−35%) precipitated from WPA upon the addition of 5% Na2CS3 and Thio-Red II, while precipitation of manganese and zinc was negligible. The water-insoluble starch xanthate adsorbed mercury (96+%), copper (38−98+%), and lead (24−75%) from 10-34-0 (N-P2O5-K2O) and WPA while adsorption of arsenic, cadmium, manganese, chromium, and zinc was negligible.