Bioleaching and biosorption behavior of vanadium-bearing stone coal by Bacillus mucilaginosus

The recovery of vanadium(V)from stone coal by bioleaching is a promising method.The bioleaching experiments and the biosorption experiments were carried out,aiming to explore the adsorption characteristics of Bacillus mucilaginosus(B.mucilaginosus)on the surface of vanadium-bearing stone coal,and the related mechanisms have been investigated.After bioleaching at 30℃ for 28 d,the cumulative leaching rate of V reached 60.2%.The biosorption of B.mucilaginosus on stone coal was affected by many factors.When the pH value of leaching system is 5.0,strong electrostatic attraction between bacteria and stone coal promoted biosorption.Bacteria in the logarithmic growth phase had mature and excellent biosorption properties.The initial bacterial concentration of 3.5×10^(8) CFU/mL was conducive to adhesion,with 38.9%adsorption rate and 3.6×10^(7) CFU/g adsorption quantity.The adsorption of B.mucilaginosus on the stone coal conformed to the Freundlich model and the pseudo-second-order kinetic model.Bacterial surface carried functional groups(-CH_(2),-CH_(3),-NH_(2),etc.),which were highly correlated with the adsorption behavior.In addition,biosorption changed the surface properties of stone coal,resulting in the isoelectric point(IEP)approaching the bacteria.The results could provide an effective reference for the adsorption laws of bacteria on minerals.

Comprehensive study on the spatial distribution of heavy metals and their environmental risks in high-sulfur coal gangue dumps in China

The accumulation of coal gangue(CG)from coal mining is an important source of heavy metals(HMs)in soil.Its spatial distribution and environment risk assessment are extremely important for the management and remediation of HMs.Eighty soil samples were collected from the high-sulfur CG site in northern China and analyzed for six HMs.The results showed that the soil was heavily contaminated by Mn,Cr and Ni based on the Nemerow index,and posed seriously ecological risk depended on the geo-accumulation index,potential ecological risk index and risk assessment code.The semi-variogram model and ordinary kriging interpolation accurately portrayed the spatial distribution of HMs.Fe,Mn,and Cr were distributed by band diffusion,Ni was distributed by core,the distribution of Cu had obvious patchiness and Zn was more uniform.The spatial autocorrelation indicated that all HMs had strong spatial heterogeneity.The BCR sequential extraction was employed to qualify the geochemical fractions of HMs.The data indicated that Fe and Cr were dominated by residual fraction;Cu,Ni and Zn were dominated by reducible and oxidizable fractions;Mn was dominated by reducible and acid-extractable(25.38%-44.67%)fractions.Pearson correlation analysis showed that pH was the main control factor affecting the non-residue fractions of HMs.Therefore,acid production from high sulfur CG reduced soil pH by 2-3,which indirectly promoted the activity of HMs.Finally,the conceptual model of HMs contamination at the CG site was proposed,which can be useful for the development of ecological remediation strategies.

Insight into modified biochars and their immobilizing effects on heavy metal(loid)s in contaminated soils: Mechanisms and influencing factors

Soil contamination by heavy metal(loid)s is a considerable environmental concern,and immobilization is a promising way to reduce toxicity.In recent years,modified/engineered biochars have gained enormous attention for their use in soil remediation,and various studies have reported notable results from their application and their ability to immobilize heavy metal(loid)s.In this review,a summary of publications on the utilization of modified biochars is presented to address the heavy metal(loid)threat in soils.Various modified/engineered biochars were described from the review of relevant publications.Modification causes great changes in biochar surface chemistry,such as increases in pore volume,surface functional groups,and metal binding sites,which can be observed through various analytical techniques,including Brunauer-Emmett-Teller,X-ray photoelectron spectroscopy,X-ray diffraction,Fourier transform infrared spectroscopy,and magnetism.Such analytical approaches elucidate immobilization mechanisms of adsorption,precipitation,surface complexation,and cation exchange between biochar and metal(loid)ions.In addition,the performance of biochar in remediating heavy metal(loid)s also leads to considerable improvements in soil conditions.Additionally,many factors that influence metal(loid)immobilization by biochar in soil,such as pH,redox potential,microorganisms,and climate regime,are highlighted.Finally,this paper emphasizes that using modified biochars as an immobilizing agent for remediation of heavy metal(loid)-polluted soils is promising and would be practicable if a comprehensive mechanism of their long-term stability in soil is well elucidated.