Removal of Arsenic, Phosphate and Chromate from Water by Iron Fumarate

Abstract

Water is often called the "universal solvent" for its ability to dissolve a wide range of chemicals. Water may therefore contain a wide variety of dissolved substances. Often, these may be toxic compounds such as arsenic which can turn groundwater into poison. Other compounds may not harm us directly, but may lead to dangerous changes in the environment (phosphorus). We have developed a family of compounds based on an iron fumarate coordination polymer. The material was synthesized in a precipitation reaction from the reaction of ferric chloride and disodium fumarate. Synthesis was carried out in water at room temperature, open to the atmosphere. The empirical formula is believed to be Fe(C4H2O4)(OH)*0.5H2O. Iron fumarate has been shown to react with phosphate, arsenate, arsenite and dichromate. It represents an advantage over other iron based materials due to ease of synthesis and high capacity for pollutants (phosphate capacity was found to be 690 mg PO43- / g iron fumarate). The capacity of iron fumarate for dichromate was found to be 26.3 mg Cr(VI) / g iron fumarate.In the case of arsenate, the material was optimized by changing the iron to fumarate ratio. Several different materials were synthesized and tested. The material synthesized that showed the highest capacity was Fe4(C4H2O4)3(OH)6 (capacity of 200.9 mg As / g iron fumarate). A relationship was then determined from four of the highest capacity materials. The relationship was used to determine the optimum iron to fumarate ratio for the reaction between iron fumarate and arsenate. The estimated optimum material is Fe5(C4H2O4)4(OH)7.