Optimization of Cr 6+ Removal by Bacillus subtilis Strain SZMC 6179J from Chromium-Containing Soil
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ORIGINAL RESEARCH ARTICLE
Optimization of Cr6+ Removal by Bacillus subtilis Strain SZMC 6179J from Chromium-Containing Soil Jianghong Liu1
•
Jian Xue1 • Xiaohang Wei1 • Huimin Su1 • Ruidan Xu2
Received: 25 September 2019 / Accepted: 11 May 2020 Ó Association of Microbiologists of India 2020
Abstract The removal rate of Cr6? has been explored by the optimized removal conditions. Five Cr-resistant strains were isolated from chromium-contained soil. The most efficient strain S1 was identified as Bacillus subtilis strain SZMC 6179J through 16S rDNA. Response surface methodology (RSM) was used to investigate the effects of four independent variables, including initial pH, initial Cr6? concentration (mg/L), time (h) and inoculation percentage (%). RSM revealed that when pH was 5.02, time was 24.0 h, inoculation percentage was 4.64% (v/v) and initial concentration of Cr6? was 55.0 mg/L, the optimal condition was obtained. Under the optimum conditions, the actual response values for Bacillus subtilis strain SZMC 6179J was 93.50%. The pH was the most significant factor towards removal rate of Cr6?. The result showed that the removal mechanism of Cr6? by Bacillus subtilis strain SZMC 6179J was reduction under normal conditions. The removal mechanism of Cr6? by Bacillus subtilis strain SZMC 6179J was adsorption under adverse conditions.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12088-020-00886-3) contains supplementary material, which is available to authorized users. & Jianghong Liu [email protected] 1
Provincial Key Laboratory of Oil & Gas Chemical Technology, College of Chemistry & Chemical Engineering, Northeast Petroleum University, Daqing 163318, Heilongjiang, China
2
School of Life Sciences, Peking University, Beijing 100871, China
Keywords Heavy metals Bioremediation Bacillus subtilis Removal conditions Response surface methodology (RSM)
Introduction With the development of industry, environment pollution has been widely concerned [1]. Serious heavy metal pollution problems have been caused through mineral resources exploitation, industrial production and other human activities [2, 3]. As a heavy metal with high toxicity, main sources of Cr are printing and dyeing, electroplating, metallurgy, chemical industry and mining wastewater [4]. In environment, chromium ions are mainly divided into Cr6? and Cr3?. Cr3? is an important trace element in the human body, mainly in the form of sediments in environment, so its hazard is small. Cr6? has carcinogenicity, mutagenicity and teratogenicity, threatening to humans, animals and the environment, and its biological toxicity is much greater than that of Cr3? [5, 6]. The treatment method of the Cr6?-containing wastewater mainly includes chemical precipitation, ion exchange, membrane separation, electrolysis and biological [7]. Chemical precipitation can accelerate the precipitation of metal ions by adding precipitant depending on the reaction characteristics of the metal ions, but it is expensive and produces a
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