School of Chemistry and Chemical Engineering, Guizhou University, Guiyang 550025, China.
School of Chemistry and Chemical Engineering, Guizhou University, Guiyang 550025, China; Collaborative Innovation Center of Guizhou Province for Efficient Utilization of Phosphorus and Fluorine Resources, Guizhou University, Guiyang 550025, Guizhou, China.
Waste Manag. 2024 May 30;181:44-56. doi: 10.1016/j.wasman.2024.04.003. Epub 2024 Apr 6.
Phosphate tailings (PT) was used to reduce the release of heavy metals (HMs) during pyrolysis and the leachable rate of residual HMs, and simultaneously improve the bioavailability of phosphorus in the sludge-based biochar. The concentration of heavy metals and the fractions determined by BCR method was used to investigate the release and the transformation of Zn, Pb, Mn, Ni and Cu during pyrolysis involved with the effects of temperature and the addition of PT. The respective pyrolysis experiments shows that the release of Zn and Pb increases with temperature for both sewage sludge (SS) and PT, and the bioavailable fractions (F1 + F2) of Mn, Ni, and Cu increases with temperature for PT. During co-pyrolysis, blended samples released lower quantities of Zn and Pb and presented lower bioavailability of HMs than the individual SS or PT. A synergistic effect of co-pyrolysis was evident for volatile Zn and Pb. The decomposition of CaMg (CO) from PT produced CaO, by which the volatile ZnCl and PbCl were transformed into ZnO and PbO with less volatility and higher reactivity with SiO and AlO than the chlorides. Then SiO and AlO from SS acted as the final stabilizer to immobilize the oxides. The final product combined with SiO and AlO, such as ZnSiO and ZnAlO, were detected. The addition of PT also introduced more Ca and P into sludge to produce biochar with higher concentration of apatite phosphorus with higher bioavailability.
磷尾矿（PT）被用于降低热解过程中重金属（HM）的释放和残留 HM 的浸出率，同时提高污泥基生物炭中磷的生物利用度。采用 BCR 法测定重金属浓度和各形态，研究了热解过程中温度和 PT 添加量对 Zn、Pb、Mn、Ni 和 Cu 释放和转化的影响。各自的热解实验表明，SS 和 PT 的 Zn 和 Pb 释放量均随温度升高而增加，PT 的 Mn、Ni 和 Cu 的可利用形态（F1+F2）随温度升高而增加。在共热解过程中，混合样品释放出的 Zn 和 Pb 量较少，且 HM 的生物利用度低于单独的 SS 或 PT。共热解对挥发性 Zn 和 Pb 具有协同作用。PT 中的 CaMg（CO）分解产生 CaO，挥发性 ZnCl 和 PbCl 转化为 ZnO 和 PbO，其挥发性和与 SiO 和 AlO 的反应性均低于相应的氯化物。然后 SS 中的 SiO 和 AlO 作为最终稳定剂将氧化物固定化。最终产物与 SiO 和 AlO 结合，如 ZnSiO 和 ZnAlO 等，被检测到。PT 的添加还将更多的 Ca 和 P 引入污泥中，产生具有更高生物利用度的磷灰石磷浓度较高的生物炭。
