基于钒、铬回收和钙循环时的含铬钒渣安全利用（英文）

Safe utilization of chromium-bearing vanadate residue by recovery of vanadium and chromium based on calcium circulation

含铬钒渣的安全经济处理是铬盐清洁化生产的关键。本文在碳酸氢钠溶液体系中,研究了钒酸钠和铬酸钠的资源化利用。结果表明:铬酸钙和钒酸钙的稳定性取决于溶液pH值和[HCO_3^-]浓度。当7.51<pH<12.32时,随着pH的升高,CaV_2O_6·4H_2O可依次转化为CaV _2O_6·2H_2O, CaV_2O_6, Ca_2V_2O_7·2H_2O和Ca_5(VO_4)_3(OH)。在NaHCO_3的稀溶液中,随着体系pH的升高和含铬钒渣加入量的减少,钒酸盐的回收率相应提高;且在较稀的NaHCO_3溶液中可取得较高的钒、铬回收率。此外,在NaHCO_3体系中加入NaOH可促进钒、铬的回收。在NaHCO_3和NaOH浓度分别为60g/L、30g/L,温度90°C,时间2 h的条件下,钒、铬的浸出率分别高达96.65%和95.40%。含铬钒渣处理后仍是危废弃,基于钙循环提出了减少处理后渣的方法。加入新鲜的处理后渣用于脱除铬酸钠中钒,比传统石灰脱钒减少60%的石灰加入量,主要原因是新鲜的CaCO_3具有活性;而铬酸钠溶液脱钒时加入焙烧的处理后渣,则不必加入石灰。随后,本文提出了含铬钒渣安全经济处理新工艺。

A safe,economical treatment of hazardous chromium-bearing vanadate residue(CVR)will significantly benefit the clean production of chromate-bearing salts.This study investigated recovery of sodium vanadate and sodium chromate from CVR in sodium bicarbonate solution.Results indicate that the stability of calcium vanadate and calcium chromate depends on pH and[HCO3?].CaV2O6?4H2O transforms into CaV2O6?4H2O,CaV2O6?2H2O,CaV2O6,Ca2V2O7?2H2O,and Ca5(VO4)3(OH)when pH increases from 7.51 to 12.32.Increasing pH and reducing CVR dosage improve the vanadate extraction rate,and high V2O5 and Na2Cr2O7?2H2O extraction rates are achieved in dilute NaHCO3 solution.Moreover,addition of NaOH positively contributes to the recovery of vanadate and chromate from CVR.Over 95%V2O5 and Na2Cr2O7?2H2O in CVR can be extracted from 60 g/L NaHCO3 and 30 g/L NaOH solutions at 90°C for 2 h.In order to reduce the hazardous residue containing chromate after recovery of CVR,calcium circulation is presented.Results show that more than 60%lime can be saved with fresh residue addition to remove vanadate from sodium chromate solution due to the active CaCO3.Moreover,no lime is required in removal of vanadate when the roasting residue is added.Therefore,a novel process is developed for utilization of CVR.