焙烧镁铝水滑石吸附脱硫废水中高浓度Cl-的基础研究

为制备镁铝摩尔比为4∶1的镁铝水滑石（LDH），实验采用共沉淀直接法，即在450 ℃温度下焙烧LDH 3 h，得到焙烧镁铝水滑石（CLHD）。取CLDH吸附剂于250 mL锥形瓶中，在一定条件下对5 000~20 000 mg/L高浓度Cl-模拟溶液及实际脱硫废水进行脱氯吸附实验和CLDH再生及重复使用性实验。探究了不同反应时间、初始浓度、反应温度、溶液的初始pH及CLDH的投加量对氯离子的脱除效果的影响，采用BET,XRD,FT-IR探究吸附机理。实验结果表明，CLHD吸附Cl-是由于层间阴离子可交换性（“结构记忆”），对Cl-吸附符合一级动力学模型，吸附量及脱氯率随反应时间的增大呈现出先快速增加后缓慢增加的趋势，吸附平衡后发生缓慢脱附反应；吸附等温线符合Freundlich方程模型，吸附量随Cl-初始浓度的增加而增大，最佳脱氯效果参数为Cl-浓度5 000 mg/L，之后随着氯离子浓度增大，由于吸附点位数量一定，脱氯率降低；CLDH对吸附Cl-的脱除率及吸附量随着温度的增加而增加，当反应温度为65 ℃时，脱氯率及吸附量最大，当温度继续升高，CLDH对Cl-的吸附效果大幅下降；改变pH值，CLDH对Cl-的吸附效果差别较小，但当pH=8时达到脱氯率及吸附量的最大值；随着CLDH投加量的增加，脱氯率逐渐变小，最佳投加量为8 g/L。65 ℃、pH=8时的实际脱硫废水脱氯实验中，CLDH脱氯率可达50.90%，一次煅烧再生CLDH脱氯率稍降，二次煅烧再生CLDH脱氯率降低约50%，CLDH对脱硫废水脱氯具可再生重复使用性。

Adsorption and ion exchange behavior of calcined Mg-Al layered double hy droxide for high concentration Cl- from flue gas desulfurization wastewater

In order to obtian the magnesium aluminum hydrotalcite (LDH) with a molar ratio of 4∶1 (magnesium:aluminum),the direct method of coprecipitation was used to calcine LDH at 450 ℃ for 3 hours to obtain the calcined magnesium aluminum hydrotalcite (CLHD).The CLDH adsorbent was taken in a 250 mL Erlenmeyer flask.Under certain conditions,dechlorination adsorption experiments and CLDH regeneration and reusability experiments were carried out on 5 000-20 000 mg/L high concentration Cl-1 simulation solution and actual desulfurization wastewater.The effects of different reaction times,initial concentration,reaction temperature,initial pH of solution and dosage of CLDH on the removal of chloride ions were investigated.The adsorption mechanism was investigated by BET,XRD and FT IR.The experimental results show that CLHD adsorbs Cl-1 due to interlayer anion exchangeability (“structural memory”),and Cl-1 adsorption conforms to the first order kinetic model.The adsorption amount and dechlorination rate increase rapidly with the increase of reaction time.After the slow increase trend,the slow desorption reaction occurs after the adsorption equilibrium; the adsorption isotherm conforms to the Freundlich equation model,and the adsorption amount increases with the increase of the initial concentration of Cl-1.The optimal dechlorination effect parameter is Cl-1 concentration 5 000 mg/L,then with the increase of chloride ion concentration,the dechlorination rate decreases due to the certain number of adsorption sites; the removal rate and adsorption capacity of CLDH for the adsorption of Cl-1 increase with the increase of temperature,when the reaction temperature is 65 ℃.The dechlorination rate and the adsorption amount are the largest.When the temperature continues to increase,the adsorption effect of CLDH on Cl-1 is greatly reduced.When the pH value is changed,the adsorption effect of CLDH on Cl-1 is small,but when the pH is 8,the dechlorination rate and the maximum amount of adsorption are reached.With the increase of CLDH dosage,the dechlorination rate gradually becomes smaller,and the optimal dosage is 8 g/L.In the dechlorination experiment of actual desulfurization wastewater at 65 ℃ and pH 8,the dechlorination rate of CLDH can reach 50.90%,the dechlorination rate of CLDH in one calcination is slightly decreased,and the dechlorination rate of CLDH in second calcination is reduced by about 50%.Desulfurization wastewater dechlorination has a reproducible reusability.