Stabilization Of Heavy Metal Cd(Ⅱ) In Oil Shale Semi-coke By Humic Acid

In the process of coal mining and ore processing,a lot of coal associated ores and wastes are produced.Oil shale semi-coke is the ash residue produced after oil shale is extracted from shale oil,which has high yield and large area.The heavy metals and radioactive elements contained in it will cause serious pollution to soil,air and groundwater due to long-term random stacking,and eventually transfer to human body through the bioaccumulation effect of the food chain,endangering human health.The prophase research team found that west fushun open-pit mine shale carbocoal produced the characteristics of heavy metal pollutants is a Cd(Ⅱ),in order to prevent the pollution of heavy metals on the mining area and the surrounding environment,it is necessary to research a kind of high efficient,low cost,no secondary pollution of heavy metals processing technology,for the mining area of soil heavy metal pollution control and repair to provide technical support.In this study,low cost and simple heavy metal stabilization repair technology was used to treat Cd(Ⅱ)in oil shale semi-coke(OS)in mining area.Humic acid was used as passivating agent and rape was used as heavy metal tolerant plant to study the stabilization effect and mechanism of humic acid on heavy metal Cd(Ⅱ)in oil shale semi-coke.The effect of humic acid stabilization on remediation of Cd(Ⅱ)contaminated soil by planting plants was evaluated.The results showed that:(1)Taking the oil shale semi-coke as the research object and the stable state Cd ratio as the investigation index,we studied the effects of humic acid(HA),fulvic acid(FA),sodium diethyldithiocarbamate[(C2H5)2NCSSNA,copper reagent for short.Among the four heavy metal passivating agents,CH]and microbial flocculant MBFA9(MBFA9),humic acid(HA)was selected to have the best passivating effect on Cd(Ⅱ)in oil shale semi-coke,and the steady state rate of Cd could reach more than 90%.(2)By means of Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),X-ray diffraction(XRD)and other characterization methods,the mechanism of HA stabilization of Cd(Ⅱ)was studied.The SEM results showed that the OS surface became rough and granular after adding HA,and it was speculated that HA and Cd(Ⅱ)formed a macromolecular structure.According to the XRD results,the main mineral composition of the samples did not change after adding HA,and there was no new characteristic peak.According to the results of FTIR analysis,the new-OH bond appeared after adding HA,which was conducive to the formation of stable chelate for Cd and increased the ratio of stable state Cd.(3)The commonly used kinetic and thermodynamic models were used to fit the adsorption process of Cd(Ⅱ).It was found that the adsorption process of Cd(Ⅱ)in oil shale semi-coke by HA under acidic conditions was consistent with the intra-particle diffusion model,and its R2 value was 0.991.The adsorption process of Cd(Ⅱ)from oil shale semi-coke by HA under neutral condition is more consistent with the quasi-first-order kinetic model,and its R2 value is 0.954.Under alkaline conditions,the R2 values of the pseudo-first-order kinetic model and particle diffusion model were 0.886 and 0.875,respectively,which were not suitable for fitting the adsorption process.Langmiur adsorption isotherm model could fit the adsorption process well,and its R2 value was 0.996,indicating that the adsorption process of Cd(Ⅱ)by HA included physical adsorption and chemical adsorption.(4)The pot experiment of three plants,including nightshade,rapeseed and honeysuckle,shows that rapeseed has the best tolerance to the oil shale semi-coke and coal associated ore soil polluted by heavy metal Cd(Ⅱ)in the west open pit mining area of Fushun.(5)After the humic acid stabilization of Cd(Ⅱ)contaminated soil,the study on the influence of planting rapeseed found that:Compared with the control group without humic acid,the ratio of stable Cd(Ⅱ)in the soil samples increased from 18%to 99%,and the germination rate increased from 94.18%to 98.33%,which promoted the height and quantity of plants,and also promoted the activities of sucrase and urease in the soil.(6)After HA was added,there were significant changes in the bacteria genera with higher relative abundance of microbial populations in the samples.Pseudarthrobacter,Sphingomonas and Clostridium in MS1 changed to Pseudomonas,Thiobacillus and Acinetobacter in MHS1.The dominant strain changed from Pseudarthrobacter to Pseudomonas.After planting rapeseed,with the change of external environment,the microbial community structure characteristics of each sample tended to be consistent,and the top three bacterial genera in abundance were basically the same.