Promotion of Ni2+ Removal by Masking Toxicity to Sulfate-Reducing Bacteria: Addition of Citrate

Abstract

The sulfate-reducing bioprocess is a promising technology for the treatment of heavy metal-containing wastewater. This work was conducted to investigate the possibility of promoting heavy metal removal by the addition of citrate to mask Ni2+ toxicity to sulfate-reducing bacteria (SRB) in batch reactors. SRB growth was completely inhibited in Ni2+-containing medium (1 mM) when lactate served as the sole carbon resource, leading to no sulfate reduction and Ni2+ removal. However, after the addition of citrate, SRB grew well, and sulfate was quickly reduced to sulfide. Simultaneously, the Ni-citrate complex was biodegraded to Ni2+ and acetate. The NiS precipitate was then formed, and Ni2+ was completely removed from the solution. It was suggested that the addition of citrate greatly alleviates Ni2+ toxicity to SRB and improves the removal of Ni2+, which was confirmed by quantitative real-time PCR targeting dissimilatory sulfite reductase (dsrAB) genes. Analysis of the carbon metabolism indicated that lactate instead of acetate served as the electron donor for sulfate reduction. This study offers a potential approach to increase the removal of heavy metals from wastewater in the single stage SRB-based bioprocess.

Synthesis of Cobalt-Nickel Nanoparticles via a Liquid-Phase Reduction Process

“…e clusters become larger, and the NP agglomerates decrease when the molar concentration of NaOH is higher than 1 M. e citric acid reacts with Ni 2+ to form Ni 2+ -citrate complexes, as shown in equation (3). It was reported that the proportion of Ni 2+ to the citrate precipitated depends on its initial concentration and pH value [40,41].…”

Review on the Use of Heavy Metal Deposits from Water Treatment Waste towards Catalytic Chemical Syntheses

“…However, the main problem with sulfide precipitation techniques is the toxicity of sulfides and hydrogen sulfides (H 2 S) gases that occurs during the precipitation process [110]. Although the process is simple, the separation process of the next stage, the slow precipitation of the metal ions and the increased cost of the filtration process, cause the techniques to be unrealistic [111]. In addition, this method fails to treat wastewater with high acid content, since it produces a large quantity of toxic sludge that needs to be treated with chemical stabilization.…”

Nickel Isotope Fractionation As an Indicator of Ni Sulfide Precipitation Associated with Microbially Mediated Sulfate Reduction

“…Although Ni is considered an essential micronutrient for plants and many other organisms, high Ni concentrations can have harmful effects on plants, micro-organisms, animals, and humans. − Metal sulfide precipitation as a remediation technique has been successfully applied to treat acid mine drainage and industrial wastewaters, and this approach has been shown to be more effective than traditional metal hydroxide precipitation. , The main advantages of sulfide precipitation include the low solubility of sulfide phases, the high rate of removal at low pH, and the potential recovery of metals from the precipitates. Sulfide precipitates are also characterized by more rapid settling rates and improved dewatering properties compared to hydroxides. , Research involving Ni sulfide precipitation at low temperatures has included both biotic − and abiotic − experiments that have resulted in the formation of a variety of Ni sulfide phases, such as α-NiS, β-NiS, Ni 3 S 4 , NiS 2 , Ni 3 S 2 , Ni 7 S 6 , and Ni 9 S 8 , depending on the experimental conditions (i.e., pH, sulfur source, reaction time). ,− …”

“…Microbially mediated reduction of sulfate under anaerobic conditions plays an important role in the treatment of waste streams contaminated by heavy metals. − , Sulfate-reducing bacteria (SRB) can couple oxidation of organic matter with dissolved sulfate reduction (eq ) resulting in metal attenuation through precipitation of metal sulfides (eq ): In contrast with abiotic sulfide precipitation, the microbially mediated process has the capacity to simultaneously remove dissolved sulfate and heavy metals, which are often problematic constituents in mining effluents and industrial wastewaters, at low cost and reduced risk . Because of these aspects, SRB have been utilized with positive outcomes in passive remediation systems, such as permeable reactive barriers (PRBs). ,− …”