二氧化钛滤柱对高砷污酸废水的吸附去除

Arsenite adsorption removal from acid wastewater using titanium dioxide adsorption filter column

冶炼废水中高浓度砷的去除及回收是环境领域面临的一大挑战。提出利用颗粒TiO_2填充滤柱对酸性废水中的高浓度砷进行连续在线吸附去除。经过3个连续串联的TiO_2滤柱,原水中高达2.5 g·L-1的三价砷可降至国家工业废水排放标准以下(<0.5 mg·L^(-1))。空床接触时间(EBCT)实验结果表明,当EBCT=20 min时滤柱中TiO_2可达到最大利用率。使用后的TiO_2颗粒可用H2SO4和Na OH进行反洗再生。X射线衍射分析结果表明,经过再生后颗粒TiO_2的晶型并未发生变化,能够实现对砷的再吸附。基于同步辐射技术的微束X射线荧光(μ-XRF)分析结果表明,反洗后少量固体残渣中有多种重金属共存。砷的K边微束X射线近边吸收结构(μ-XANES)表明固体残渣中存在五价砷,说明反洗过程中三价砷部分氧化。固体残渣可以通过化学提纯的方式实现砷及多种共存重金属的回收。再生废液可与原酸性废水混合调p H至中性后重新进入滤柱进行吸附去除。提出的利用颗粒TiO_2处理酸性冶炼废水的新方法可有效去除废水中的高浓度三价砷,吸附剂可重复利用,同时可以实现砷及其他重金属的回收,整个工艺流程几乎不产生废渣,对环境友好的同时可产生经济效益。

Remediation of metallurgical industry wastewater has presented a great environmental challenge for decades. In this study,a remediation technique for As（ Ⅲ） adsorptive removal,adsorbent regeneration,and As（ Ⅲ） recovery was proposed. Using three granular TiO2 columns in series,As（ Ⅲ） with initial concentration of 2. 5 g·L^-1 could be reduced to below the wastewater discharge limit of 0. 5 mg·L^-1. Optimization of the empty bed contact time（ EBCT） suggested that a 20 min EBCT was sufficient for As（ Ⅲ） removal. The spent TiO2 could be regenerated using H2SO4 and Na OH. The X-ray diffraction patterns of pristine and spent TiO2 reveal no change in the crystalline structure,which ensures its high effectiveness after regeneration and enables its reuse.Synchrotron-radiation-based micro-beam X-ray fluorescence（ μ-XRF） was used to analyze the in situ elemental composition of the solid residue after regeneration,revealing the coexistence of many heavy metals. Arsenic Kedge micro-focus X-ray absorption near-edge structure（ μ-XANES） analysis suggested the existence of As（ Ⅴ） in the solid residue,indicating that strong alkali conditions during the regeneration process may facilitate the oxidation of As（ Ⅲ）. The small amounts of solid residue produced during the adsorbent regeneration process may be used as a raw material for the production of arsenic compounds. The waste solution can be further treated after mixing with raw water to adjust the pH to neutral. This adsorption,regeneration,and reuse process provides aninnovative technique for metallurgical industry wastewater remediation that is promising for practical applications.