溶液pH对钒钨离子交换吸附分离的影响规律

Influence Law of Solution pH on Separation of Vanadium and Tungsten by Ion Exchange Adsorption

采用阴离子交换树脂对废SCR脱硝催化剂NaOH浸出液的模拟液进行钒钨选择性分离,主要考察了溶液pH变化对树脂吸附钒钨行为的影响。结果表明,在碱性条件下溶液pH变化对W的吸附影响相对较小,但对V的吸附影响显著。在pH从8增大到12的过程中,V的主要离子形态由V_4O_(12)^(4-)转化为HVO_4^(2-),被树脂吸附的能力大幅减弱;当pH从12增大至14时,OH^-浓度增大成为影响钒钨吸附的主要因素,由于上柱能力WO_4^(2-)>VO_4^(3-)>OH^-,OH^-浓度的增大对V吸附的抑制效果也更明显,导致V吸附进一步减弱。随着pH从8增大到14,W/V分离系数从0.146增大到2.36。当溶液pH=14时,负载树脂采用1mol/L NaOH+2mol/L NaCl混合溶液进行洗脱,W的最大解吸浓度可达84g/L,V最大不超过2g/L,在一定程度上实现了钨钒分离,并使W得到一定程度的富集,解吸液可作为后续钙沉或结晶工艺的母液。

Abstract.Selective separation of vanadium and tungsten from the simulated NaOH leaching solution of waste SCR denitration catalyst by anion exchange resin was studied. The effect of solution pH change on adsorption behavior of vanadium and tungsten onto the resin was investigated. The experimental results show that solution pH change has little influence on W adsorption under the alkaline condition,but has re- markable influence on V adsorption. When pH increases from 8 to 12, the main ion form of V is trans- formed from V4O12^4- to HVO4^2- , resulting in greatly reduced adsorption ability of V onto the resin. When pH increases from 12 to 14,the increase of OH^- concentration becomes the main factor affecting the ad- sorption of V and W. Due to the adsorption capacity of WO4^2-〉VO4^3-〉OH^- ,the inhibition effect of in- creased OH^- concentration on V adsorption is more obvious,resulting in further weakening of V adsorp- tion. As pH increases from 8 to 14,W/V separation coefficient increases from 0. 146 to 2.36. When pH is equal to 14 and the loaded resin is eluted with a mixed solution of 1 mol/L NaOH ＋ 2 mol/L NaCl,the maximum desorption concentration of W can reach 84 g/L,while the maximum value of V is not more than 2 g/L. As a result,the separation of tungsten and vanadium is achieved to some extent,tungsten is enriched to a certain extent,and the desorbed liquid can be used as a mother liquid for the subsequent calcium pre- cipitation or crystallization process.