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Heavy metal contamination of mine tailings is one of the most serious environmental challenges facing the mining industry worldwide. Conventional technologies used for the treatment of such tailing soils are expensive both in terms of operation and capital costs as well as being not so effective. In the present study, an indigenous calcifying urease producing bacterial strain was isolated from copper mine tailing soil and used for bioimmobilization of copper, lead and cadmium in contaminated mine tailing soils. Phylogenetic analysis of the 16S rRNA gene sequence identified it asBacillus firmus. The efficiency of metal bioimmobilization was based on microbially induced calcite precipitation (MICP). A five-stage sequential soil extraction procedure was carried out to obtain distribution patterns for the different metals. The mobility of the toxic metals was found to be significantly reduced in the exchangeable fraction with their concentrations markedly increasing in the carbonated fraction after bioremediation. Scanning electron microscopy showed the precipitation of calcite in association with the bacterial cells. Calcium carbonate minerals such as calcite, gwihabaite and aragonite were identified in the bioremediated tailings soils using X-ray diffraction (XRD). It is concluded that MICP holds considerable promise for the remediation of mine tailing soils by efficient immobilization of toxic metals such as copper, lead and cadmium. [ABSTRACT FROM AUTHOR]

Simultaneous removal of antibiotic tetracycline hydrochloride (TC) and As(III) by poorly-crystalline Mn dioxide was investigated. TC and As(III) can be effectively oxidized and removed by MnO 2 . High concentrations of TC and As(III) competed with each other for oxidation or adsorption sites on MnO 2 and thus affected their removal efficiency. The intermediates and products of TC after reaction with poorly-crystalline manganese dioxide were identified by LC–ESI–MS (liquid chromatography–electrospray ionization–mass spectrometry), and the decomposition pathways of TC by MnO 2 were proposed. This study is helpful for understanding the importance of environmental Mn dioxides in the decontamination of combined pollution by organic pollutants and metal(loid)s. [ABSTRACT FROM AUTHOR]