Abstract
In response to the insufficient supply of carbon sources and the toxicity of heavy metal ions when using sulfate reducing bacteria (SRB) to treat acid mine wastewater (AMD), the immobilized particles are prepared with Rhodopseudomonas, SRB and lignite as the main raw materials. And based on single factor test and orthogonal test to determine the optimal ratio of biologically activated lignite fixed SRB particles. The adsorption characteristics of immobilized particles were studied under the optimal ratio, and the reaction kinetics and adsorption capacity of SRB particles immobilized on biologically activated lignite to different ions were analyzed. The results show that: lignite not only has good adsorption performance, but also can be used as the carbon source of SRB after being degraded by Rhodopseudomonas, solving the problems of low removal efficiency of SRB treatment of AMD and insufficient carbon source supply. When the dosage of lignite (particle size is 200 mesh), Rhodopseudomonas, and SRB are 3%, 10%, and 10% mesh, the prepared biologically activated lignite-immobilized SRB particles have the best effect on AMD treatment. The removal rates of SO42−, Zn2+, and Cu2+ were 83.21%, 99.59%, and 99.93%, respectively, the pH was increased to 7.43, the COD release was 523 mg/L, and the ORP value was − 134 mV. The reduction process of SO42− by the biologically activated lignite-immobilized SRB particles conforms to the pseudo-first-order kinetics, and the adsorption of Zn2+ is more in line with the Freundlich isotherm adsorption equation and the pseudo-second-order kinetic model. And it does not spread in a single form, both internal and external diffusion occur. SEM, FT-IR, and BET analysis of biologically activated lignite immobilized SRB particles showed that the pore structure is developed, has a large number of adsorption sites, and some activated groups participate in the reaction. The adsorption process of Zn2+ and Cu2+ in AMD meets the multi-layer adsorption theory.
Highlights
Mining activities make sulfide ore contact with oxygen to form AMD containing heavy metal ions ( Zn2+, Cu2+, etc.) and high SO42− content[1], which will have a serious impact on the environment[2,3]
Microbial immobilization technology can reduce the toxic effects of heavy metal ions and acidity on sulfate reducing bacteria (SRB), but it is still necessary to add the carbon source required for the growth of SRB when preparing immobilized p articles[19]
Lignite is rich in oxygen-containing functional groups, such as carboxyl, alcoholic hydroxyl, phenolic hydroxyl, quinone, carbonyl, and m ethoxy[22], and heavy metal ions are combined with oxygen-containing functional groups on the surface of lignite
Summary
Serial number SO42− Mean value 1 SO42− Mean value 2 SO42− Mean value 3 SO42− Range Cu2+ Mean value 1 Cu2+ Mean value 2 Cu2+ Mean value 3 Cu2+ Range Zn2+ Mean value 1 Zn2+ Mean value 2 Zn2+ Mean value 3 Zn2+ Range pH Mean value 1 pH Mean value 2 pH Mean value 3 pH Range COD Mean value 1 COD Mean value 2 COD Mean value 3 COD Range ORP Mean value 1 ORP Mean value 2 ORP Mean value 3 ORP Range. The results show that the influence of each factor on pH is not significant This may be due to the relatively small degree of freedom of error in this experiment, which reduces the sensitivity of the orthogonal test results, which conceals the significance of the orthogonal test results. Source of variance SO42− Sum of squares of deviations SO42− Free Degree SO42− Mean Square SO42− F value SO42− P value SO42− Significant Cu2+ Sum of squares of deviations Cu2+ Free Degree Cu2+ Mean Square Cu2+ F value Cu2+ P value Cu2+ Significant Zn2+ Sum of squares of deviations Zn2+ Free Degree Zn2+ Mean Square Zn2+ F value Zn2+ P value Zn2+ Significant pH Sum of squares of deviations pH Free Degree pH Mean Square pH F value pH P value pH Significant
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