Abstract：
Compared with the post-treatment of pollutants, such as the removal of phosphate from wastewater, it is more important to develop effective emission control strategies to reduce phosphate pollution. Phosphogypsum (PG) is a typical solid waste byproduct of phosphate production and contains high amounts of residual phosphate. In order to control the phosphate emissions during the recycling of PG aggregates for cemented backfill, another solid waste product—iron tailings (ITs)—was added during the preparation of backfill slurry. The results showed that the ITs effectively accelerated the phosphate removal in cemented PG backfill, enabling the quick reduction in the phosphate concentration to the discharge standard (<0.5 mg/L) within 15 min. This means that the emissions of phosphate to bleeding water were effectively controlled. The adsorption experiment showed that phosphate was adsorbed by the ITs, and the adsorption data fitted well with the Langmuir adsorption model (R2 = 0.98) and pseudo-second-order kinetic model (R2 = 0.99), indicating that the phosphate adsorption of ITs was a monolayer chemical adsorption. Furthermore, an unconfined compressive strength (UCS) test was performed on the backfill with the addition of ITs. Compared to the control group (without ITs), the UCS of backfill with 20% ITs increased from 1.08 MPa to 1.33 MPa, indicating that the addition of solid waste could be beneficial to the strength development of the backfill by mitigating the interference of phosphate with the hydration process. The backfill cured for 28 d was selected for the toxic leaching test, and the phosphate concentration in the leachates was always below 0.02 mg/L, indicating that ITs can effectively immobilize phosphate in backfill for a long time.
摘要：
与污染物的后处理相比，例如从废水中去除磷酸盐，制定有效的排放控制策略以减少磷酸盐污染更为重要。磷石膏（PG）是磷酸盐生产的典型固体废物副产品，含有大量残留的磷酸盐。为了控制胶结回填PG骨料回收过程中的磷酸盐排放，在制备回填浆料的过程中添加了另一种固体废物-铁尾矿（ITs）。结果表明，ITs有效地促进了胶结PG回填土中磷酸盐的去除，能够在15分钟内将磷酸盐浓度快速降低到排放标准（＆lt;0.5mg/L）。这意味着磷酸盐向渗水的排放得到了有效控制。吸附实验表明，磷酸盐被ITs吸附，吸附数据与Langmuir吸附模型(R2=0.98)和拟二级动力学模型(R2=0.99)拟合良好,表明ITs的磷酸盐吸附是单层化学吸附。此外，无侧限抗压强度（UCS）测试是在回填添加IT。与对照组(无ITs)相比，20%ITs回填的UCS从1.08MPa增加到1.33MPa，表明固体废物的添加可以通过减轻磷酸盐对水合过程的干扰来有利于回填的强度发展。选择固化28d的回填土进行有毒浸出试验，渗滤液中的磷酸盐浓度始终低于0.02mg/L，表明ITs可以长期有效地固定回填土中的磷酸盐。
