采用水合氧化铁吸附钨酸钠溶液中的钒及其吸附特性

Vanadium adsorption from sodium tungstate solution and its adsorption characteristics using hydrous ferric oxide

利用水合氧化铁的吸附特性,研究从钨酸钠溶液中吸附除钒。运用模型量化在不同pH、表面负荷以及离子强度条件下的水合氧化铁对钒的吸附特性。研究结果表明:在含有不同质量浓度的钨、钒溶液中,当钒的初始质量浓度为24 mg/L,钨的初始质量浓度分别为50,98,213和466 mg/L时,钒在水合氧化铁上最大的吸附平台出现的pH范围为2~10,钨对应的最大pH吸附范围分别为2.0~8.2,2.0~7.8,2.0~7.0和1.7~2.0。在钨与钒的质量比为1000的钨酸钠溶液中,直接在钨酸钠中生成水合氧化铁的方式作为吸附剂比水合氧化铁的吸附效果更好;除钒率随着水合氧化铁用量增加而增加,但钨损率也随之增加;在水合氧化铁的量为钒物质的量的40倍、pH为9.8~10.8、反应1 h的条件下,除钒率高于99%而钨损率维持在1.85%~4.42%;以此做扩大实验后得到在结晶率为96%和100%的仲钨酸铵中,铁质量分数分别为6×10^(−6)和9×10^(−6),满足0级仲钨酸铵的铁含量标准。钒在水合氧化铁上的吸附几乎不受离子强度的影响,采用表面配位模型模拟水合氧化铁吸附钒的行为,并确定水合氧化铁的3种酸位,其酸位常数分别为3.50,7.54和11.02。

The adsorption characteristics of hydrous ferric oxide were used to study the vanadium removal in sodium tungstate solution.The model was used to quantify the adsorption characteristics of vanadium on hydrous ferric oxide at different pH,surface loadings and ionic strengths.The results show that when the vanadium initial mass concentration is 24 mg/L and W initial mass concentrations are 50,98,213 and 466 mg/L,the vanadium adsorption maximum appears at pH of 2.0 to 10.0 and the tungsten adsorption maximum appears at pH of 2.0 to 8.2,2.0 to 7.8,2.0 to 7.0,and 1.7 to 2.0 respectively.The adsorption is more effective when hydrous ferric oxide is generated directly in the sodium tungstate solution with the mass ratio of tungsten to vanadium of 1000.When the addition amount of hydrous ferric oxide is increased,the vanadium removal ratio is higher while the tungsten loss ratio is lower.Under the conditions that the amount of substance of hydrous ferric oxide is 40 times of vanadium,pH is 9.8−10.8 and reaction time is 1 h,the vanadium removal ratio is higher than 99%while the tungsten loss ratio maintains 1.85%−4.42%.The results of scale-up experiment are that the Fe mass fractions in ammonium paratungstate with crystallization ratios of 96%and 100%are 6×10^(−6) and 9×10^(−6) respectively,which meet the Fe content standard of 0-level ammonium paratungstate.Ionic strength has very minor or no impact on the adsorption of vanadium.Speciation-based model can simulate the adsorption of vanadium on hydrous ferric oxide in a broad pH range and surface loading conditions.Three surface acid sites of hydrous ferric oxide are identified and their acidity constants of acid sites are 3.50,7.54 and 11.02 respectively.