4种碱基添加剂对1,2,4-三氯苯污染土壤热脱附效果的影响

含氯有机物是土壤中常见的污染物质，对人体危害大，采用热脱附修复技术去除。通过改变加热温度、加热时间及添加4种碱性物质 (NaHCO₃、NaOH、Ca(OH)₂、CaCO₃) 等条件获取TCB的去除效率及污染土壤理化性质变化情况。实验结果表明，热脱附能有效去除土壤中TCB，当温度为350 ℃加热30 min时，污染土壤中TCB去除率为83.27%；碱性物质的添加能有效强化热脱附过程，添加1%的NaHCO₃、NaOH、Ca(OH)₂和CaCO₃后，TCB去除率分别提高了28.28、26.13、20.28、18.19%。碱性物质的添加促进了TCB的脱氯和降解，相比于无碱性物质热脱附，添加1%NaHCO₃和NaOH后尾气中DCBz增加了5.4 ug·L⁻¹和3.65 ug·L⁻¹。热脱附后土壤有机碳、有效磷质量分数和阳离子交换量减少，电导率增大；碱基协同热脱附前后土壤的总有机碳质量分数变化不大，土壤中有效磷质量分数和阳离子交换量明显增大，脱附条件为250 ℃、30 min以及1%的Ca(OH)₂时，脱附前后有效磷由57.5 mg·kg⁻¹增大至80.2 mg·kg⁻¹，阳离子交换量由19.72 cmol⁺·kg⁻¹增大至24.4 cmol⁺·kg⁻¹。本研究结果可为热脱附技术修复三氯苯污染土壤提供技术参考。

Effects of four base additives on thermal desorption of 1,2,4-trichlorobenzene contaminated soil

Chlorinated organic matter is a common pollutant in soil, which is harmful to human body. It is removed by thermal desorption remediation technology. The removal efficiency of TCB and the change of physical and chemical properties of contaminated soil were obtained by changing the heating temperature, heating time and adding four kinds of alkaline substances (NaHCO3, NaOH, Ca(OH)2 and CaCO3). The experimental results showed that thermal desorption colud effectively remove TCB from soil. When the temperature was 350 ℃ for 30 min, the TCB removal rate was 83.27%. The addition of alkaline substances colud effectively enhance the thermal desorption process. After adding 1% NaHCO3, NaOH, Ca(OH)2 and CaCO3, the TCB removal rates are increased by 28.28, 26.13, 20.28 and 18.19%, respectively. The addition of alkaline substances promoted the dechlorination and degradation of TCB. Compared with the thermal desorption of non-alkaline substances, the DCBz in the tail gas increased by 5.4 ug·L−1 and 3.65ug·L−1 after the addition of 1%NaHCO3 and NaOH. After thermal desorption, the mass fraction of organic carbon, available phosphorus and cation exchange capacity of soil decreased, while the electrical conductivity increased. The mass fraction of total organic carbon (TOC) in soil did not change much, but the mass fraction of available phosphorus and cation exchange capacity in soil increased significantly When the desorption conditions were 250 ℃, 30min and 1% Ca(OH)2, The available phosphorus concentration increased from 57.5 mg·kg−1 to 80.2 mg·kg−1, and the cation exchange capacity increased from 19.72 cmol+·kg−1 to 24.4 cmol+·kg−1. The results can provide technical reference for the remediation of trichlorobenzene contaminated soil by thermal desorption.