Ferrous bio-oxidation byAcidithiobacillus ferrooxidansin hydrochloric acid pickling waste liquor

Abstract

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 .