Continuous changes in electrical conductivity of sodium aluminate solution in seeded precipitation

铝酸钠溶液种分过程中电导率的连续变化规律(英文)

The mechanism of seeded precipitation of sodium aluminate solution was studied by measuring the seeded-precipitation rate and electrical conductivity online, as well as calculating the activity and fraction of ion pair. The results show that the electrical conductivity of sodium aluminate slurry linearly decreases with increasing aluminum hydroxide addition. Moreover, both the electrical conductivity of slurry and the difference in electrical conductivity between sodium aluminate solution and slurry remarkably decline in the first 60 min before gradually increasing in the preliminary 10 h and finally reaching almost the same level after 10 h. In low Na2 O concentration solution the activities of Na OH and Na Al（OH）4 in seeded precipitation are high, which can enlarge the difference in conductivity between slurry and solution. Additionally, more ion pairs exist in solution in preliminary seeded precipitation, and the adsorption of Na＋Al（OH）4- on seed surface is likely to break the equilibrium of ion pair formation and to decrease the difference in conductivity in preliminary seeded precipitation.

通过在线测定种分过程铝酸钠溶液的电导率,计算种分过程中组分的活度和缔合度,研究铝酸钠溶液的种分机理。结果表明:浆液电导率随着氢氧化铝含量增加呈线性降低;种分初期60 min内浆液电导率和铝酸钠溶液和浆液电导率的差值均显著降低,然后随种分的进行而显著升高,但在10 h后电导率增大幅度变小。低浓度溶液中Na OH和Na Al(OH)4活度较高,有利于种分,使溶液和浆液间电导率差值增大;且种分初期溶液中离子对多,有利于Na+Al(OH)4-吸附在晶种表面,导致溶液中生成离子对的平衡被打破,从而使电导率差值减小。