典型重金属离子对羟基磷酸钙结晶法回收污水中磷的影响

The single and combined effects of three heavy metal ions (Cu²⁺, Cd²⁺, Zn²⁺) on phosphorus recovery from the simulated phosphorus-rich supernatant in municipal wastewater plant by crystallization of hydroxyapatite (HAP) were investigated. And Visual MINTEQ (Ver3.2) was applied for auxiliary analysis. The results indicated that Cu²⁺, Cd²⁺ or Zn²⁺ could inhibit HAP crystallization for phosphorus removal, and Zn²⁺ showed the strongest inhibition effect which fitted Monod inhibition model equation with the inhibition constant of 178.0 mg·L⁻¹. The HAP crystallization system could synergistical remove heavy metals, and the order of the removal rate was Cu²⁺>Cd²⁺>Zn²⁺. Joint addition of Cu²⁺, Cd²⁺ and Zn²⁺ could strengthen the inhibition of phosphorus removal and weaken the removal effect of single heavy metal ion. SEM observation showed that the dosing of Cu²⁺, Cd²⁺ and Zn²⁺ led to the loose surface of the products, while they had similar impacts on the morphology of the products. The simulation results of Visual MINTEQ confirmed that Cu²⁺, Cd²⁺ and Zn²⁺ inhibited phosphorus removal by grabbing crystal ions of HAP and formed precipitate with heavy metal impurity, and the order of the impurity content was Cu²⁺>Cd²⁺>Zn²⁺. These results can provide reference for the practical application of HAP crystallization method in phosphorus recovery in urban sewage.