磷灰石在废水治理中的应用

由于具有特殊的晶体化学特点，天然磷灰石可以作为一种新型环境功能矿物材料用于对含重金属废水的处理。对Cd^2 ,Pb^2 ,Fe^2 ,[UO2]^2 ,Cu^2 ,Zn^2 ,Cr^6 ,和Hg^2 等离子的吸附实验结果表明，磷灰石对绝大多数重金属离子去除效果很好。在室温和pH为3、作用时间为60min的实验条件下，Pb^2 去除率可达99．4％，饱和吸附容量超过1100mg/g。主要的去除机理包括吸附、表面络合、溶解－沉淀以及重金属离子与晶格中之间的离子交换作用。一般而言，被吸附的重金属离子可固化在晶格中而不出现解吸，因此不会产生二次污染。影响去除效果的因素包括磷矿石的类型、磷灰石的矿物成分、介质pH值、温度、吸附时间、离子的初始浓度、样品的粒度和用量等。通常，羟基磷灰石的效果优于氟磷灰石的，硅质磷块岩的效果优于钙质磷块岩的，结构碳酸根的存在能量增加比表面积从而增加反应活性。对于不同离子，最佳pH值条件不同。温度的升高有利于反应的快速进行，但一般地说60－180min即可达到平衡。

APPLICATIONS OF MINERAL APATITES IN THE TREATMENT OF WASTE WATER

The present paper is concerned with the applications of minearal apaties A10[XO4]6Z2. Due to the particular crystal-chemical characteristics, mineral apatites including synthetic hydroxyapatite, fluorap-atite and natural mineral carbonate-fluorapatite can be used as excellent environmental function materials for treatment of heavy-metal and F- ions in waste water. The experimental results for aqueous Cd2+, Pb2+, Fe2+, [UO2]2+, Cu2+, Zn2+, Cr6+, Hg2+and F-show that apatites could remove effectively most of the heavy-metal ions from solution. Take the removal of Pb2+ by natural carbonate-fluorapatite as an example. Under the conditions of room-temperature, pH = 3 and action time of ca. 60 min,the attenuation ratio is 99. 4% and attenuated Pb2+ more than 1 100 mg per 1 g sample. Removal mechanisms include ad-sorption-sorption of cations on the apatites, surface-complexation, dissolution-precipitation and ion-exchange between the aqueous cations and the lattice Ca2+. The cations attenuated could be fixed into the lattice of apatite without re-dissolving that results in secondary pollution. The major factors affecting the attenuated effect include the types of phosphorite, mineral chemical composition of apatites, pH value in the solutions, conditioning time, initial concentration of aqueous heavy-metal ions, and the sample size and amount. In general, the hydroxyapatite shows a more active property than that of fluorapatite; siliceous phosphate is more effective than calciferous phosphate; the exist of structural carbonate could increase the specific area and the activity of sample. For different cations, the optimum pH value is different; increasing of action temperature would favour the removal rate but the balance time is generally 60-180 min.