Mechanism of Molybdenum Migration and Transformation in the Tailings and Soils in the Luanchuan Mining Area

doi:10.19657/j.geoscience.1000-8527.2023.096

Abstract

Abstract:

To investigate the controls of the molybdenum (Mo) pollution sources in the Luhun Reservoir, we conducted a field survey with collecting six Mo tailing ponds.Molybdenum speciation analysis and leaching experiments were performed to study the mechanism of Mo migration and transformation in the tailings and soils.The average Mo content in the six samples of tailings and soils are 238.24 and 125.88 mg/kg, respectively, and the Mo content in the leached solution is 0.26 mg/L.Tessier extracting result shows that the Mo residual in the tailing was 97.71%, while together with that, the exchangeable and carbonate bound Mo in the soil are 63.66%, 22.35%, and 11.80%, respectively.After the leaching experiments with acid to alkaline rainfalls, the Mo residual in the tailing decreased.The neutral and alkaline rainfall favor the transformation of Mo residual to carbonate Mo bound, leading to the carbonate Mo bound increasing from 1.19% to 18.85%, and then to 24.14%.This indicates that the neutral and alkaline rainfall can enhance the transporting capability of Mo.In the soils, the iron-manganese oxidation state and the organic Mo bound increased largely, and all the other Mo species decreased by different degree with the acid rainfall leaching.The residual and the organic Mo bound increased and the carbonate Mo bound and the iron-manganese oxidation state decreased largely with the lea-ching of neutral-alkaline rainfall.It suggested that the acid rainfall can increase the formation of the molybdate of iron and manganese, while the neutral and alkaline rainfall likely favor the formation of the iron and manganese hydroxide and carbonate, which prevents the formation of the iron and manganese molybdate, enhancing the transporting capability of Mo by an order of magnitude.Although the differences of the ore and the physicochemical properties of the tailings and the soils can cause different Mo transportation and transformation, the acid to alkaline rainfall can enhance the transportation and transformation of Mo in the two media, and hence affect the soil and aqueous environments.

Key words: molybdenum tailing, soil, molybdenum, rainfall leaching, speciation, Luanchuan mining area

CLC Number:

P595

PAN Feifei, CHEN Hongwei, CHEN Danli, ZHAO Lü, LI Zhengzui, CHEN Hui, PENG Xiangxun, LIU Jing. Mechanism of Molybdenum Migration and Transformation in the Tailings and Soils in the Luanchuan Mining Area[J]. Geoscience, 2024, 38(03): 755-763.

Figures/Tables 6

Fig.1 Tectonic framework of the Qinling Orogen belt (a)[15] and the geological background and location of deposits in the study area (b)[16]

Fig.2 Flow chart of the laboratory experiments

Table 1 Heavy mental concentrations in the molybdenum tailing and the extracted liquid (mg/L)

区域	Mo	Cr	Cd	Cu	Pb	Zn	W	As	Hg	Ni
6座尾矿库尾渣平均含量	238.240	0.017	0.460	58.720	9.280	135.830	262.370	5.910	0.017	28.870
三道庄钼矿尾渣	195.000	51.200	0.300	62.100	15.000	69.700	103.000	0.530	0.017	24.000
三道庄钼矿尾渣浸出液	0.176	ND	ND	ND	ND	ND	ND	ND	ND	0.002

Table 2 Analytcal results of Mo speciation in the molybdenum tailings and soils

介质	项目	可交换态	碳酸盐结合态	铁锰氧化态	有机态	残渣态	合计
尾渣	含量(mg/kg)	0.94	10.18	7.98	0.50	836.00	855.60
尾渣	占比(%)	0.11	1.19	0.93	0.06	97.71	100
土壤	含量(mg/kg)	31.60	16.68	3.02	0.08	90.00	141.38
土壤	占比(%)	22.35	11.80	2.14	0.05	63.66	100

Fig.3 Effect of different pH values in rainwater on the Mo concentrations over time in leachate of molybdenum tailings (a) and soils (b)

Fig.4 Change of Mo speciation in the molybdenum tailings (a) and the soils (b) after the eluviating

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