新型赤泥基钝化剂的制备及其氮、磷缓释性能与镉钝化效应

Preparation of new red mud based passivators and their nitrogen and phosphorus release characteristics and cadmium passivation effect

采用结晶法制备了6种新型赤泥基钝化剂并对其进行表征分析,通过淋溶试验和土壤培养试验探究了新型赤泥基钝化剂的氮、磷元素释放特性及其对土壤镉的钝化效果。表征结果表明添加了生物炭的3种赤泥基钝化剂中生物炭的加入改变了晶体的孔隙结构并使得表面形成平滑且紧密的外层结构,这将更有利于氮、磷元素的缓慢释放。淋溶试验结果表明,加入改性赤泥、生物炭和尿素的赤泥基钝化剂的氮、磷缓释效果优于其他赤泥基钝化剂。其中加入热改性赤泥、生物炭和尿素的赤泥基钝化剂(RMCN)和加入酸改性赤泥、生物炭和尿素的赤泥基钝化剂(SMCN)的第10次淋溶液中总磷质量浓度分别为8.21、8.26 mg/L,总氮质量浓度分别为44.77、44.37 mg/L,明显高于其他组。土壤镉污染钝化试验结果发现SMCN和RMCN的钝化效果较好,使有效态镉含量分别降低了61.38%和54.20%。综合表征分析、土柱淋溶试验和土壤培养试验结果发现,加入酸改性赤泥、生物炭和尿素的钝化剂综合效果最优。

In this study,six new red mud based passivators were prepared by crystallization method and characterized.The release characteristics of nitrogen and phosphorus and the passivation effect of soil cadmium on the new red mud based passivators were explored through leaching experiment and soil culture experiment.The characterization results showed that the biochar changed the structure of crystal pores and formed a smoother and tighter outer layer structure on the surface in the three red mud based passivators with biochar,which would be more conducive to the slow release of nitrogen and phosphorus elements.The results of leaching experiments showed that the slow release effect of red mud based passivator with modified red mud,biochar and urea on nitrogen and phosphorus was better than that of other red mud based passivators.The total phosphorus concentrations were 8.21 mg/L and 8.26 mg/L,respectively,and the total nitrogen concentrations were 44.77 mg/L and 44.37 mg/L,respectively,in the tenth leaching solutions of the red mud based passivator with heat-modified red mud,biochar and urea(RMCN)and with acid-modified red mud,biochar and urea(SMCN),which were significantly higher than those in the other groups.The results of soil cadmium pollution passivation experiment showed that the available cadmium content was reduced by 61.38%by SMCN,and the available cadmium content was reduced by 54.20%by RMCN.Based on the results of characterization analysis,soil column leaching experiment and soil culture experiment,it was found that the comprehensive effect of the passivator with acid-modified red mud,biochar and urea was the best.