Performance of sulphonic cation exchangers in the recovery of ammonium from basic and slight acidic solutions

摘要

Two sulphonated polystyrene-divinylbenzene cation exchangers (gel type Purolite SGC 100 x 10 MBH and macroporous Purolite C160 MBH) have been investigated for NH_4~+ ions uptake from the ammonium-rich simulated solutions, corresponding to the caustic condensate of the nitrogen fertilizers production. One component (NH_3 or NH_4NO_3) solutions and the mixtures with varying molar ratio of these compounds have been used at the total concentration 0.214 mol/L. Batch and column experiments have been conducted to establish the influence of the matrix structure on the performance of the cation exchangers investigated during the sorption and the desorption. Batch sorption isotherms and breakthrough curves have shown the similar behaviour of the cation exchangers in the removal of NH_4~+ and NH_3. On decreasing the influent pH from 11.4 to 5.74 a decrease in breakthrough capacity (BC) from 2.57 to 1.93 mol/L was observed. The distribution coefficients (K_d), calculated from the batch sorption isotherms, are higher for the basic feed solution than for slightly acidic one. Both the degree of the cation exchanger regeneration (N/N_0) and the efficiency of the NH_4~+ ions recovery (N_R), obtained using 0.7 bed volume (BV) of eluent (20% nitric acid) are lower for Purolite C 160 MBH than those for Purolite SGC 100 x 10 MBH. Using 5 BV of eluent the efficiency of the ammonium recovery amounted to 100% for both cation exchangers investigated. With respect to the efficiency of NH_4~+ ions sorption and regeneration cation exchangers investigated are applicable for the recovery of ammonium ions from caustic condensate in the nitrogen fertilizers production.