In this study, an effective circulating system was developed to remove heavy metals in medical waste incineration (MWI) fly ash. MWI fly ash (MWIFA)-column experiments were performed to remove Cu, Pb, Zn, Cd and Ni from MWIFA using EDTA disodium (Na₂EDTA). Iron-column experiments were conducted to study the removal effect of zero-valent iron on the five heavy metals from washing wastewater. TCLP test method was employed to evaluate heavy metals toxicity of MWIFA residues generated after 0-0.2 mol/L Na₂EDTA solution treated. After washed by 0.2 mol/L Na₂EDTA solution, TCLP leaching values of Cu, Pb, Zn, Cd and Ni were the lowest and satisfied the standard (GB 5085.3–2007), and the leaching values were 58.4±2.0 mg/L, 2.81±0.14 mg/L, 64.3±4.0 mg/L, 0.156±0.005 mg/L, 0.381±0.006 mg/L. Concentrations of Cu, Pb, Zn, Cd and Ni in iron-column effluent were reduced by 99.7%, 91.6%, 91.6%, 75.4% and 75.7%, respectively. Na₂EDTA was recovered and recycled to the removal of heavy metals from MWIFA. Compared new Na₂EDTA solution with recycled Na₂EDTA solution, recycled Na₂EDTA and water could be reutilized to dispose MWIFA. The removal efficiencies of Cu, Pb, Zn, Cd and Ni by recycled 0.2 mol/L Na₂EDTA solution were 67.1%, 68.8%, 63.2%, 73.9%, 50.7%, respectively, the removal efficiencies that using recovered Na₂EDTA decreased by 2.6%, 3.9%, 3.3%, 4.2%, and 1.6%, respectively. Successive batch experiments were also conducted to evaluate industrialization potential and reusable times for recycled Na₂EDTA. After 4 recirculation cycles, extraction efficiencies of Pb and Cd (removal efficiency at different cycles divided by removal efficiency of new Na₂EDTA) declined towards 80%.

IMPLICATIONS

An effective circulating system was developed to remove heavy metals in MWI fly ash (MWIFA). Integration of Na₂EDTA with Fe⁰ promoted the removal of heavy metals from MWIFA. Na₂EDTA, NaCl and water were stepwise extracted from iron-column effluent, respectively. Recovered Na₂EDTA can still effectively remove heavy metals from MWIFA. Results from this research indicated that this circulating system possessed industrialization potential.

在这项研究中，开发了一种有效的循环系统以去除医疗废物焚烧（MWI）粉煤灰中的重金属。进行了MWI粉煤灰（MWIFA）柱实验，使用EDTA二钠（Na ₂ EDTA）从MWIFA中去除Cu，Pb，Zn，Cd和Ni 。进行了铁柱实验，研究了零价铁对洗涤废水中五种重金属的去除效果。采用TCLP测试方法评价了0-0.2 mol / L Na ₂ EDTA溶液处理后产生的MWIFA残留的重金属毒性。用0.2 mol / L Na ₂洗涤后EDTA溶液中，铜，铅，锌，镉和镍的TCLP浸出值最低，满足标准（GB 5085.3-2007），浸出值为58.4±2.0 mg / L，2.81±0.14 mg / L，64.3 ±4.0 mg / L，0.156±0.005 mg / L，0.381±0.006 mg / L。铁塔流出物中的铜，铅，锌，镉和镍的浓度分别降低了99.7％，91.6％，91.6％，75.4％和75.7％。回收Na ₂ EDTA，并将其循环用于从MWIFA中去除重金属。将新的Na ₂ EDTA溶液与回收的Na ₂ EDTA溶液进行比较，可以将回收的Na ₂ EDTA和水重新利用以处置MWIFA。循环0.2 mol / L Na ₂对Cu，Pb，Zn，Cd和Ni的去除效率EDTA溶液的去除率分别为67.1％，68.8％，63.2％，73.9％，50.7％，使用回收的Na ₂ EDTA的去除率分别降低了2.6％，3.9％，3.3％，4.2％和1.6％。还进行了连续的批生产实验，以评估回收的Na ₂ EDTA的工业化潜力和可重复使用时间。在4个循环周期后，Pb和Cd的提取效率（不同循环的去除效率除以新的Na ₂ EDTA的去除效率）降至80％。

含义

开发了有效的循环系统以去除MWI粉煤灰（MWIFA）中的重金属。Na ₂ EDTA与Fe ^0的结合促进了MWIFA中重金属的去除。从铁柱流出物中逐步提取Na ₂ EDTA，NaCl和水。回收的Na ₂ EDTA仍然可以有效地去除MWIFA中的重金属。这项研究的结果表明，这种循环系统具有工业化潜力。