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• Five elution methods and optimal elution conditions of cyanide tailings were investigated. • Four reagents were screened to promote the elution of cyanide tailings, and the optimal proportion of these four reagents was determined as 5:2:2:1. • The combination of reagent elution and positive pressure filtration for synergistic elution improved the elution efficiency of cyanide. • The combined elution strategy was applied to engineering and achieved desired results. At present, the cyanide gold extraction process is still the main technology for gold production. Generated cyanide tailings containing highly toxic substances exhibit potential environmental risks. These tailings are in urgent need of purification treatment, especially after being classified as hazardous waste. In this study, the impacts of elution methods, operating time, tailings/water ratios, reagent types on the elution rates of cyanide were investigated. Furthermore, the composite elution method developed in this research was extended for engineering. Results showed that the optimum elution conditions were determined to be: stirring elution, tailings/water ratio (M/V ; 1:1) and operating time (10-20 min). Besides, 4 reagents (sodium dodecyl benzene sulfonate, cyclodextrin, sodium silicate and calcium hydroxide) were selected from four categories of 21 reagents for further composite elution. The cyanide elution rate was the highest (90.7%±0.1%) while the molar ratio of these 4 reagents was 5:2:2:1. Moreover, the combination of reagent elution and positive pressure filtration improved the elution efficiency of cyanide (92.6%±0.8%). And the cyanide content in the toxic leaching solution was lower than the standard value (5.0 mg/L). Furthermore, the composite elution method developed in this study was also extended for engineering. The concentration of cyanide in the leachate was < 5.0 mg/L, and was stable during 189 days of detection. Notably, the effluent can be reused directly, or reused after further treatment. The zero discharge of effluents and solid wastes was realized in the processes. The above results provided supports for the engineering treatment of cyanide tailings. [Display omitted] [ABSTRACT FROM AUTHOR]

Penicillium oxalicum SL2 (SL2) is a previously screened Pb-tolerant fungus that can promote crops growth. The relationship between SL2 colonization and Pb immobilization was studied to provide a theoretical basis for microbial remediation of Pb-contaminated paddy soil. In this study, green fluorescent protein (GFP) labeled SL2 was inoculated into different Pb-contaminated paddy soils (S1-S6). The Pb extracted from the soil by HNO 3 , EDTA and CaCl 2 were used to characterize the available Pb. The results showed that the colonization of SL2 was divided into lag phase (0-7 days), growth phase (7-30 days), and mortality phase (30-90 days). SL2 colonized well in sandy soils rich in clay and total phosphorus with initial pH of 4.5-7.0. In addition, SL2 increased soil pH and decreased soil Eh, which was beneficial to immobilize Pb. In different soils, the highest percentages of CaCl 2 -Pb, EDTA-Pb, and HNO 3 -Pb immobilized by SL2 were 34.34%-40.53%, 17.05%-20.11%, and 7.39%-15.62%, respectively. Pearson correlation analysis showed that the percentages of CaCl 2 -Pb and EDTA-Pb immobilized by SL2 were significantly positively correlated with the number of SL2 during the growth phase. SL2 mainly immobilized Pb in the growth phase and a higher peak number of SL2 was beneficial to the immobilization of Pb. [Display omitted] [ABSTRACT FROM AUTHOR]

Oxidation remediation is a commonly used technology for PAHs contaminated soil presently, but the overestimate of efficiency due to ongoing remediation by residual oxidants during extraction and testing has not been paid enough attention. In this study, persulfate was activated by Fe(II) to investigate the effects of residual oxidants on PAHs removal during detection process and the elimination effects of adding Na 2 SO 3 and extending sampling time on residual oxidants. Results verified that the residual oxidants removed PAHs in extraction process, making the results lower than the actual values: the detection recovery rate η of ∑PAHs and 3-6 ring PAHs ranged from 24.3% (25% Na 2 S 2 O 8 treatment) to 87.4% (5% Na 2 S 2 O 8 +4/4Fe2+ treatment), 20.1%-99.0%, 28.9%-87.9%, 20.8%-89.4%, and 18.6%-76.9%, respectively. After adding Na 2 SO 3 , the accuracy of detection results increased significantly: the η of ∑PAHs and 3-6 ring PAHs increased to 64.1%-96.5%, 58.8%-95.5%, 73.8%-114.4%, 60.6%-95.6%, and 45.4%-77.1%, respectively. After 49 days of adding oxidants, residual oxidants had no considerable effect on the detection of PAHs, indicating it was appropriate to start soil remediation verification sampling49 days after the remediation was completed. The observed results will help scientific evaluation of the remediation effects of chemical oxidation on organic contaminated soil. [Display omitted] [ABSTRACT FROM AUTHOR]