碱液对填埋场浓缩液中Ca^(2+)、Mg^(2+)的去除效果研究

REMOVAL EFFICIENCY OF Ca^(2+), Mg^(2+) FROM CONCENTRATED LEACHATE IN LANDFILL USING NaOH SOLUTION

为了减缓浓缩液蒸发过程设备的腐蚀和结垢问题,研究了碱液及复配药剂对浓缩液中Ca^(2+)、Mg^(2+)的去除率,并利用多种技术手段分析表征了沉淀产物的化学组成和矿物特性,探究了Ca^(2+)、Mg^(2+)的去除对浓缩液水质参数和结垢量的影响。结果表明:1)当7.5 mol/L NaOH溶液投加体积比为3%,反应时间60 min时浓缩液中Ca^(2+)、Mg^(2+)得以有效去除,其去除率分别为89.49%和98.45%,但此条件下沉淀物的沉降性能较差。2)复配实验表明,NaOH溶液与硅藻土、Ca(OH)_(2)复配时,显著提高了沉淀产物的沉降性能,且Ca^(2+)、Mg^(2+)去除率未受到显著影响;添加1%Ca(OH)_(2)时沉降效果最为显著,沉降比降为36.84%,明显低于单独碱液(NaOH)的75.61%。3)对碱液沉淀产物进行化学组成和矿物特性分析可知,沉淀产物主要含有Mg(OH)_(2)、Mg_(5)(CO_(3))_(4)(OH)_(2)·4H_(2)O、NaCl以及KCl等矿物。4)对浓缩液原液和碱液处理后上清液进行模拟蒸发发现,调节pH至5.0时碱液处理后结垢量低于浓缩液原液。

In order to reduce and alleviate the corrosion and scaling of equipment during the evaporation process of concentrated leachate,the removal efficiency of Ca^(2+)and Mg^(2+)in concentrated leachate was investigated by the combination of alkali solution and compound reagents.The chemical composition and mineral characteristics of precipitates were analyzed by various methods.The influence of water quality parameters and scaling amount during the removal of Ca^(2+)and Mg^(2+)were also explored.The results showed that:1)when the volume addition ratio of 7.5 mol/L NaOH was 3%,the Ca^(2+)and Mg^(2+)were effectively removed after 60 min of reaction,and the removal efficiencies were 89.49%and 98.45%respectively,but the sedimentation performance was poor under this condition;2)when NaOH combined with diatomite and Ca(OH)_(2) was used,the sedimentation performance of precipitates was significantly improved,and the removal efficiency of Ca^(2+)and Mg^(2+)were not significantly affected.The sedimentation ratio was 36.84%when 1%Ca(OH)_(2) was added,significantly lower than single NaOH solution of 75.61%.3)according to the analysis of chemical composition and mineral characteristics of precipitates,the main minerals were Mg(OH)_(2),Mg_(5)(CO_(3))_(4)(OH)_(2)·4 H_(2)O,NaCl and KCl;4)the simulated experiment for evaporation of raw concentrated leachate and supernatant showed that the amount of scaling after alkali treatment was lower than that of raw concentrated leachate when pH was adjusted to 5.0.