イオン交換樹脂を含む懸濁水への難溶性無構化合物の溶解(第5報) : リン酸アンモニウムマグネシウム
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概要
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Dissolution of MgNH_4PO_4・6 H_2O(MAP) in an; aqueous suspension containing H-R (a strongly acidic ion exchange resin) leads to the formation of intermediate products o wing to the selectivity of cation exchange reaction. The process was studied by measuring the changes in pH and k(specific conductivity), and the quantities of eluted ions such as Mg^<2+> NH_4^+ and PO_4^<3->. These results have led to the assumption that the dissolution process consists of the following reactions ; 1) Initial stage, the dissolution proceeds with 100% PO_4^<3-> and ca. 30% Mg^<2+> in fractional solubility up to 1.52-1.78 of reaction molar ratio, H-R/MAP. The fact which the pH of the solution was kept at 7.0 suggests the formation of equimolar compounds consist of HPO_4^<2-> and H_2PO_4^<->as shown in Eq. (1) , 3 MgNH_4 PO_4+5(H-R) → Mg(H_2PO_4)_2+ (NH_4)_2H PO_4+2(Mg-R_2)+NH_4-R (1) 2) Soluble Mg(H_2PO_4)_2 reacts subsequently with H-R accompaning by the decrease in Mg^<2+> concentration and increase in the acidity, Mg(H_2PO_4)_2+2(H-R) → Mg-R_2+2H_3PO_4 (2) 3) The increase in acidity causes to convert of (NH_4)_2HPO_4 with releasing NH_3 to yield NH_4OH in water. 4) Neutralization brings about a depletion in concentration of both [H^+] and [OH^-] having high equivalent conductivity, which results a decrease in k level. 5) The reaction (1) and (2) may be combined into the overall reaction (3), which, unlike the dissolution promoted by a mineral acid, is characterized by the intermediate steps, 2MgNH_4PO_4 + 6(H-R) → 2(Mg-R_2)+2(NH_4-R)+3H_3P O_4 ( 3 )
- 1990-09-01
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