Veeken Adrie H M, Akoto Lawrence, Hulshoff Pol Look W, Weijma Jan
Department of Environmental Technology, Wageningen Agricultural University, PO Box 8129, 6700 EV Wageningen, The Netherlands.
Water Res. 2003 Sep;37(15):3709-17. doi: 10.1016/S0043-1354(03)00262-8.
Precipitation of Zn2+ with S2- was studied at room temperature in a continuously stirred tank reactor of 0.5l to which solutions of ZnSO4 (800-5800 mgl(-1) Zn2+) and Na2S were supplied. The pH was controlled at 6.5 and S2- concentration in the reactor was controlled at set point values ranging from 3.2x10(-19) to 3.2x10(-4) mgl(-1), making use of an ion-selective S2- electrode. In steady state, the mean particle size of the ZnS precipitate decreased linearly from 22 to 1 microm for S2- levels dropping from 3.2x10(-4) to 3.2x10(-18) mgl(-1). At 3.2x10(-11) mgl(-1) of S2-, the supplies of ZnSO4 and Na2S solutions were stoichiometric for ZnS precipitation. At this S2- level, removal of dissolved zinc was optimal with effluent zinc concentration <0.03 mgl(-1) while ZnS particles formed with a mean geometric diameter of about 10 microm. Below 3.2x10(-11) mgl(-1) of S2- insufficient sulfide was added for complete zinc precipitation. At S2- levels higher than 3.2x10(-11) mgl(-1) the effluent zinc concentration increased due to the formation of soluble zinc sulfide complexes as confirmed by chemical equilibrium model calculations.
在室温下，于一个0.5升的连续搅拌釜式反应器中研究了Zn²⁺与S²⁻的沉淀反应，向该反应器中供应ZnSO₄（800 - 5800毫克/升Zn²⁺）和Na₂S溶液。利用离子选择性S²⁻电极将pH控制在6.5，并将反应器中的S²⁻浓度控制在3.2×10⁻¹⁹至3.2×10⁻⁴毫克/升的设定值范围内。在稳态下，对于S²⁻水平从3.2×10⁻⁴降至3.2×10⁻¹⁸毫克/升，ZnS沉淀的平均粒径从22微米线性减小至1微米。当S²⁻浓度为3.2×10⁻¹¹毫克/升时，ZnSO₄和Na₂S溶液的供应对于ZnS沉淀是化学计量的。在此S²⁻水平下，溶解锌的去除效果最佳，出水锌浓度<0.03毫克/升，同时形成的ZnS颗粒的平均几何直径约为10微米。当S²⁻浓度低于3.2×10⁻¹¹毫克/升时，添加的硫化物不足以使锌完全沉淀。当S²⁻浓度高于3.2×10⁻¹¹毫克/升时，如化学平衡模型计算所证实的，由于形成了可溶性硫化锌络合物，出水锌浓度增加。
