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A B S T R A C THydrochloric acid pickling waste liquor (PWL HCl ) is generated in the steel surface cleaning treatment. This process is used to chemically remove the iron oxide scale from steel. PWL HCl is classified as toxic and hazardous waste in many countries because it contains high concentrations of corrosive hydrochloric acid, ferrous irons, and other heavy metals. These properties pose difficulties for PWL HCl reclamation and bioavailability of toxic metals in general. The oxidation of ferrous to ferric sediment is a possible route for PWL HCl reclamation. In this study, Acidithiobacillus ferrooxidans (At.f) was applied to PWL HCl to investigate ferrous oxidation efficiency under low pH and high chloride ion stress. Results indicated that the oxidation ability of At.f remained relatively high when PWL HCl and 9K medium mixed ratio to 60% (V/V); the species was able to endure the extreme conditions at pH 1.4, ferrous ions 0.04 mol/L, chloride ion 800 mg/L, and maintain the ferrous oxidation rate at 90%. The pH was a critical factor impacting the ferrous oxidation efficiency. Different types of mineral crystal shapes, determined by SEM, illustrated the possibility of a new mineral formation. XRD analysis revealed main composition of minerals as (NH 4 ) Fe 3 (SO 4 ) 2 (OH) 6 , and infrared spectroscopy indicated that the existence of C-Cl bond promoted the adaptation of bacteria to PWL HCl .

The technology of driving along goaf has been widely used in the prevention of high ground stress and coal-gasoutburst in coal mining in our country. In this paper, the 11-2 Coal Seam of zhujixi coal mine is taken as the research object. Based on the test of drilling cuttings and residual gas content at different depths of solid coal at the goaf side and the research on the distribution law, it is concluded that the effective pressure relief drainage belt width at the goaf side of 11-2 Coal Seam after mining is 29m. Field practice has been carried out in the adjacent working face. The results show that the predicted indexes measured during the coal roadway driving period do not exceed the specified critical value, which verifies the rationality of the width of the discharge zone. The results provide a theoretical support for the reasonable layout of the continuous working face, improve the driving speed of the coal roadway, reduce the cost of gas control, improve the economic benefits of the mine, and ensure the safety production of the mine.