Abstract
Removal of phosphate ion in swine urine is a big concern for an environmental conservation. To solve the problem, phosphate ion absorbent in swine urine was developed using carboxymethy cellulose (CMC) and iron compounds. Mixing CMC with iron salt aqueous solutions resulted in gels as known well. While the gel formation proceeded instantaneously when CMC and ferric salt [Fe(III)] aqueous solution were mixed, the gel was not formed immediately when ferrous salt [Fe(II)] aqueous solution was used. Oxidation of Fe (11) to Fe (Ill) occurs gradually in Fe(II) aqueous solution. However, addition of CMC to the Fe(II) solution promoted the oxidation to Fe (Ill). The rate of gel formation could be controlled by addition of acid to CMC-Fe(II) mixture. The absorbent made of CMC and Fe(II) seemed to be more effective than that made of CMC and Fe(III), in Fe content and phosphate ion removal. The resultant gels reduced the phosphorus content from 457 to 3 mg/l in artificial urine and from 78 to 2 mg/1 in swine urine, respectively. The values fulfill the regulation of effluent from the pigsty.
