School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK.
School of Civil Engineering, University of Leeds, Leeds LS2 9JT, UK.
Sci Total Environ. 2018 Dec 1;643:1191-1199. doi: 10.1016/j.scitotenv.2018.06.272. Epub 2018 Jul 4.
Vanadium is a toxic metal present in alkaline leachates produced during the weathering of steel slags. Slag leaching can therefore have deleterious effects on local watercourses due to metal toxicity, the effects of the high pH (9-12.5) and rapid carbonation (leading to smothering of benthic communities). We studied the fate and behaviour of V in slag leachate both through field observations of a heavily affected stream (Howden Burn, Consett UK) and in controlled laboratory experiments where slag leachates were neutralised by CO ingassing from air. V was found to be removed from leachates downstream from the Howden Burn source contemporaneously with a fall in pH, Ca, Al and Fe concentrations. In the neutralisation experiments pH reduced from 12 → 8, and limited quantities of V were incorporated into precipitated CaCO. The presence of kaolinite clay (i.e. SiOH and AlOH surfaces) during neutralisation experiments had no measureable effect on V uptake in the alkaline to circumneutral pH range. XANES analysis showed that V was present in precipitates recovered from experiments as adsorbed or incorporated V indicating its likely presence in leachates as the vanadate oxyanion (HVO). Nano-scale particles of 2-line ferrihydrite also formed in the neutralised leachates potentially providing an additional sorption surface for V uptake. Indeed, removal of V from leachates was significantly enhanced by the addition of goethite (i.e. FeOOH surfaces) to experiments. EXAFS analysis of recovered goethite samples showed HVO was adsorbed by the formation of strong inner-sphere complexes, facilitating V removal from solution at pH < 10. Results show that carbonate formation leads to V removal from leachates during leachate neutralisation, and the presence of both naturally occurring and neoformed Fe (oxy)hydroxides provide a potent sink for V in slag leachates, preventing the spread of V in the environment.
钒是一种有毒金属，存在于碱性浸出液中，这些浸出液是在钢渣风化过程中产生的。因此，由于金属毒性、高 pH 值（9-12.5）和快速碳化（导致底栖生物窒息），渣浸出液会对当地水道造成有害影响。我们通过对一个受严重影响的溪流（英国康塞特的豪登溪）的实地观测以及通过在空气中通入 CO2 中和渣浸出液的控制实验室实验，研究了钒在渣浸出液中的归宿和行为。在豪登溪源头下游，随着 pH 值、Ca、Al 和 Fe 浓度的下降，V 从浸出液中被去除。在中和实验中，pH 值从 12 降至 8，有限量的 V 被掺入沉淀的 CaCO3 中。在中和实验中，高岭石粘土（即 SiOH 和 AlOH 表面）的存在对碱性至近中性 pH 范围内的 V 吸收没有可测量的影响。XANES 分析表明，从实验中回收的沉淀中存在吸附或结合的 V，这表明钒可能以钒酸盐氧阴离子（HVO）的形式存在于浸出液中。在中性化浸出液中还形成了纳米尺度的 2 线水铁矿颗粒，这可能为 V 的吸收提供了额外的吸附表面。事实上，通过向实验中添加针铁矿（即 FeOOH 表面），可以显著增强从浸出液中去除 V。对回收针铁矿样品的 EXAFS 分析表明，HVO 通过形成强内球配合物被吸附，从而在 pH<10 时促进 V 从溶液中去除。结果表明，在浸出液中和过程中，碳酸盐的形成导致浸出液中 V 的去除，而天然存在和新形成的 Fe（氧）氢氧化物的存在为渣浸出液中的 V 提供了一个强大的汇，防止 V 在环境中扩散。
