【作者】 王维；

【导师】 杜冬云；

【作者基本信息】 中南民族大学 ， 环境化学， 2021， 硕士

【摘要】 磷石膏（PG）是湿法磷酸生产过程中磷矿粉与硫酸反应后经淋洗过滤分离得到的一种工业废渣,主要由Ca SO₄·2H₂O组成,同时还含有残酸、可溶性磷、氟以及重金属等有害杂质,具有酸性强、杂质多、资源化利用难度大的特点。近年来,我国的磷石膏年产量维持在70-80 Mt左右,堆存总量超过500 Mt,并且堆存量还在逐年增加。大量的磷石膏堆存不仅造成土地浪费,也给环境带来了严重污染。因此,寻找经济、高效的方法对磷石膏进行大规模消纳处理,具有重大的现实意义。铜尾渣（CSS）是铜冶金（造锍熔炼）过程中产生的大宗工业固废。2018年,我国铜尾渣产量高达18 Mt。铜尾渣中SiO₂含量一般在30%以上,但CaO含量少,通过添加钙源和强碱活化,可表现出胶凝性能。目前,铜尾渣只有部分被回收利用于水泥生产和有价金属的回收,部分则被堆存在露天堆场内,由于其含有铜、铅、锌等重金属,易对周边土壤和水体环境造成重金属污染,具有环境风险。本文对铜尾渣、磷石膏的基本理化性质进行了研究,并通过向磷石膏/铜尾渣混合体系中添加NaOH作为激发剂、CaO作为额外钙源,加入25-35%（wt.%）的水,搅拌均匀后压制成具有一定抗压强度的固结体（PG-S）,实现了铜尾渣对磷石膏的高效固定/稳定化处理。实验结果表明:（1）参照标准方法,对磷石膏和铜尾渣进行毒性浸出。新鲜磷石膏浸出液中PO₄^3-、F^-浓度分别高达831.13 mg/L和196.08 mg/L;铜尾渣中Zn、Pb、As的浸出浓度分别为165.19 mg/L、28.76 mg/L、6.95 mg/L,超过了《危险废物鉴别标准毒性浸出标准》（GB5085.3-2007）限值,Cu、Cr、Cd的浸出浓度超过了《综合污水排放标准》（GB8978-1996）限值。（2）CaO的添加对磷石膏中PO₄^3-、F^-的固定具有重要作用,单独利用铜尾渣对磷石膏进行固定/稳定化处理得到的固结体PG-S中PO₄^3-、F^-的浸出浓度分别为27.78 mg/L、48.95 mg/L,添加CaO后PG-S中PO₄^3-、F^-的浸出浓度分别降到了0.07 mg/L和3.70 mg/L。此外,适量的NaOH添加使PG-S的抗压强度得到了较大提升,同时对PO₄^3-、F^-的固定也有一定促进作用。（3）按体系中SiO₂/Na₂O摩尔比为1.89/1添加NaOH,根据体系中可溶性PO₄^3-、F^-含量添加CaO,以不同的磷石膏/铜尾渣质量配比对磷石膏进行处理。当质量配比为5:1时,PG-S 28 d无侧限抗压强度达到18.9 MPa;质量配比为20:1、10:1、5:1时,Zn、Pb、As等重金属浸出浓度和PO₄^3-、F^-浸出浓度均可达到《污水综合排放标准》（GB8978-1996）一级排放标准要求。当配比达到2:1、1:1,由于铜尾渣和NaOH添加量的增加,PG-S中重金属的浸出风险增加,Pb、Zn的浸出浓度未能达到排放标准要求。（4）通过XRD、SEM、XPS、FTIR表征分析发现,体系中C-S-H、钙矾石的产生,为PG-S提供了强度;磷石膏中PO₄^3-、F^-与铜尾渣中Pb、Zn发生共沉淀反应,对PO₄^3-、F^-、Pb、Zn起到了稳定化作用,地球化学模拟结果显示,PG-S中可能会生成羟基磷灰石（Hydroxyapatite,Ca₅（PO₄）₃OH）、萤石（Fluorite,Ca F₂）、Pb₅（PO₄）₃OH（Hydroxyl pyromorphite）、Pb₃（PO₄）₂、Zn₃（PO₄）₂·4H₂O等沉淀物。此外,模拟结果显示随着体系p H的上升,可能会导致Pb、Zn固定效果下降。更多还原

【Abstract】 Phosphoric acid is usually produced by two different approaches:by pyrometallurgy or by hydrometallurgical method.Waste phosphogypsum（PG）is a by-product generated from the wet-process phosphoric acid production which is based on the chemical reaction of phosphate rock with sulfuric acid.PG mainly consists of calcium sulfate dehydrate（Ca SO₄·2H₂O）,making up over 90%,in association with various amounts of hazardous substances such as residual acid,soluble phosphate,fluoride and heavy metals.PG has the characteristics of strong acidity,major impurities and difficult to utilize as resource.In recent years,the annual production of PG in China was in the range of 70-80 million tons.At present,the stock of PG in China exceeds 500 million tons,and it is increasing gradually.Large amount of PG storage not only generates land waste,but also results in serious environmental contamination of soil,water,and atmosphere.Therefore,finding an economic and efficient way to achieve large-scale consumption of phosphogypsum has great application value.Copper smelting slags（CSS）are solid waste produced from the process of pyrometallurgical copper production.In 2018,the production of CSS was 18 million tons in China.Generally,the content of SiO₂in CSS is more than 30%.As CaO content increases or under the activation of NaOH,CSS can exhibit cementitious properties and can be used as partial or full replacement for Portland cement.In fact,only part of CSS was reused in cement production or for valuable metal recovery,while other parts are dumped in storage piles.Due to the heavy metal contents such as copper,lead,and zinc,it could easily cause heavy metal pollution to the surrounding soil and water environment showing environmental risk.Through the study of physical and chemical properties,we found the synergistic effect between CSS and PG.In this study,a small amount of NaOH and CaO were added to the mixed slag of PG and CSS as activator and additional calcium sources.After mixing with 25～35%（Wt.%）water,it was pressed to produce cemented blocks（named PG-S）with certain compressive strength,which realized the efficient synergistic solidification/stabilization（S/S）of PG by CSS.The results showed that:1.According to the standard method,the leaching toxicity of PG and CSS were assessed.The concentrations of PO₄^3-and F^-in the leaching solution of fresh PG were 831.13 mg/L and 196.08 mg/L,respectively;the leaching concentrations of Pb,Zn and As of CSS were 165.19 mg/L,28.76 mg/L and 6.95 mg/L,respectively,which exceeded the limits of Identification standard of hazardous waste-Identification of leaching toxicity（GB 5085.3-2007）,and the leaching concentrations of Cr,Cu and Cd exceeded the limits of Integrated wastewater discharge standard（GB8978-1996）.2.The addition of NaOH and CaO could enhance the S/S behavior of PO₄^3-and F^-.The addition of CaO reduced the leaching concentration of PO₄^3-and F^-from 27.78 mg/L and 48.95 mg/L to 0.07 mg/L and 1.70mg/L,respectively;the addition of NaOH reduced the leaching concentration of PO₄^3-and F^-to 1.04 mg/L and 35.27 mg/L,respectively.3.Phosphogypsum was treated by CSS under different PG/CSS mass ratio.By adding NaOH,the mole ratio of SiO₂/Na₂O in the PG/CSS system was equal to 1.89.CaO was added according to the content of soluble PO₄^3-and F^-in the system.When the mass ratio of PG/CSS was5:1,the 28 d UCS of PG-S was 18.9 MPa;when the mass ratio of PG/CSS was 20:1,10:1 and 5:1,the leaching concentration of heavy metals such as Zn,Pb,As and the leaching concentration of PO₄^3-and F^-meet the first grade of Integrated wastewater discharge standard（GB8978–1996）.When the ratio increased to 2:1 and 1:1,the leaching risk of heavy metals in PG-S also increased due to the increase of CSS and NaOH addition,and the leaching concentrations of Pb and Zn failed to meet the requirements of emission standard.4.XRD,SEM,XPS and FTIR analysis showed that the formation of C-S-H and Ettringite in the PG/CSS system provided strength for the PG-S;the co-precipitation reaction of PO₄^3-and F^-with Pb and Zn stabilized PO₄^3-,F^-,Pb and Zn.The geochemical modeling was consistent with the characterization results,and the simulation showed that with the increase of p H,the fixation effect of Pb and Zn may decrease.更多还原