A Biotechnological Strategy for Molybdenum Extraction Using Acidithiobacillus ferrooxidans

U mobilization and associated U isotope fractionation by sulfur-oxidizing bacteria

Uranium (U) contamination of the environment causes high risk to health, demanding for effective and sustainable remediation. Bioremediation via microbial reduction of soluble U(VI) is generating high fractions (>50%) of insoluble non-crystalline U(IV) which, however, might be remobilized by sulfur-oxidizing bacteria. In this study, the efficacy of Acidithiobacillus (At.) ferrooxidans and Thiobacillus (T.) denitrificans to mobilize non-crystalline U(IV) and associated U isotope fractionation were investigated. At. ferrooxidans mobilized between 74 and 91% U after 1 week, and U mobilization was observed for both, living and inactive cells. Contrary to previous observations, no mobilization by T. denitrificans could be observed. Uranium mobilization by At. ferrooxidans did not cause U isotope fractionation suggesting that U isotope ratio determination is unsuitable as a direct proxy for bacterial U remobilization. The similar mobilization capability of active and inactive At. ferrooxidans cells suggests that the mobilization is based on the reaction with the cell biomass. This study raises doubts about the long-term sustainability of in-situ bioremediation measures at U-contaminated sites, especially with regard to non-crystalline U(IV) being the main component of U bioremediation.

Diphasic Sheeting Device with Cyanex-301 for Dislodging Feature of Divalent Cadmium from Industrial Effluent

A novel diphasic sheeting device (DSD) including complemental feeding stage and complemental disintegrating stage for dislodging features of Cd(II), was investigated. The complemental feeding stage included feeding liquor and Bis(2,4,4 trimethylamyl) dithiophosphonic acid (Cyanex-301) as the carrier in petroleum, and the complemental disintegrating stage included Cyanex-301 as the carrier in petroleum and hydrochloric acid as the disintegrating reagent. The impacts of volumetric ratio of sheeting liquor and feeding liquor(S/F), initial molarity of Cd(II) and ion intensity of the feeding liquor, pH, volumetric ratio of sheeting liquor and disintegrating reagent (S/D), molarity of hydrochloric acid liquor, Cyanex-301 molarity in the complemental disintegrating stage on dislodging of Cd(II), the virtues of DSD compared to the traditional sheeting device, the constancy of system, the reuse of sheeting liquor, and the retention of the sheeting stage were also investigated. Experimental results illustrated that the optimum dislodging conditions of Cd(II) were achieved as hydrochloric acid molarity was 4.00 mol/L, Cyanex-301 molarity was 0.150 mol/L, and S/D was 1:1 in the complemental disintegrating stage, S/F was 1:10, and pH was 5.00 in the complemental feeding stage. The ion intensity of the complemental feeding stage had no distinct impact on the dislodging feature of Cd(II). When initial Cd(II) molarity was 3.20 × 10^-4 mol/L, the Cd(II) dislodging percentage was up to 92.9% in 210 min. The dynamic formula was inferred on the basis of the theorem of mass transferring and the interfacial chemistry.

Study on Di-Phase Membrane Device with DZ272(DDD) for Purification Behavior of Divalent Cobalt Ions in Slops

A novel Di-phase membrane device with DZ272 (DDD) containing a replenishing feed section and replenishing resolving section for the purification behavior of Co(II) has been studied. The replenishing feed section was composed of feed solution and Di-isooctylphosphinic acid (DZ272) as the carrier in fossil oil, and the replenishing resolving section was composed of DZ272 as the carrier in fossil oil and HCl as the resolving agent. The effects of the voluminal ratio of the membrane solution and feed solution (O/F), pH, initial molarity of Co(II) and ionic strength in the feed solution, voluminal ratio of membrane solution and resolving agent (O/S), molarity of H₂SO₄ solution and DZ272 molarity in the replenishing resolving section on purification of Co(II) were considered. The benefits of DDD compared to the traditional membrane device, system stability, reuse of the membrane solution and retention of the membrane section were also studied. Experimental results indicated that the optimal purification conditions of Co(II) were obtained, as H₂SO₄ molarity was 2.00 mol/L, DZ272 molarity was 0.120 mol/L, O/S was 3:1 in the replenishing resolving section, O/F was 1:8 and pH was 5.20 in the replenishing feed section. The ions intensity in the replenishing feed section had no apparent effect on purification behavior of Co(II). When the initial Co(II) molarity was 3.00 × 10^-4 mol/L, the purification percentage of Co(II) achieved 93.6% in 200 min. The kinetic equation was deduced in light of the law of mass diffusivity and interfacial chemistry.

High-Temperature Reaction Mechanism of Molybdenum Metal in Direct Coal Liquefaction Residue

In this paper, the extraction residue of direct coal liquefaction residue-DCLR(ER) was used as raw material. The high-temperature reaction mechanism of Mo compound in DCLR(ER) was investigated using a synchronous thermal analyzer and the Factsage database. The high temperature reaction of DCLR(ER)-MoO3 in an oxygen atmosphere consists of pyrolysis of organic components at 400–600 °C, molybdenum trioxide sublimation at 747–1200 °C, and a stable stage at 600–747 °C. The thermal reaction process of the DCLR(ER)-MoS2 system in the oxygen atmosphere involves the pyrolysis of unreacted coal and asphaltene, the oxidation of molybdenum sulfide at 349–606/666 °C, the diffusion of MoO3 at 606/666–85 °C, and the sublimation reaction process of MoO3 at 854–1200 °C. The results show that the lower heating rate can promote the oxidation of the Mo compound and the sublimation of molybdenum trioxide. On the other hand, the oxides of aluminum, calcium, and iron in DCLR(ER) can inhibit the oxidative pyrolysis efficiency of the DCLR(ER)-MoS2 system.

Effects of Unconventional Water Agricultural Utilization on the Heavy Metals Accumulation in Typical Black Clay Soil around the Metallic Ore

Unconventional water is an important water resource for agricultural utilization in the drought and water shortage of Northeast China. Additionally, exploration in making full use of it is an important way to alleviate water shortage in China. This paper analyzed the effects of unconventional water through field trials on the accumulation of heavy metals in both cucumbers and the typical black clay soil (expressed as black soil) around the Anshan metallic ore. By exploring the effects of unconventional water after secondary treatment on the accumulation characteristics of heavy metals in cucumbers and the heavy metal balance in the soil-crop system under different conditions, the study shows that there are no significant differences in the heavy metal content when the quantity of unconventional water for irrigation varies. Unconventional water for short-term irrigation does not cause pollution to either the soil environment or the crops. Nor will it cause the accumulation of heavy metals, and the index for the heavy metal content is far below the critical value of the trade standard and national standard, which indicates that the crops irrigated with unconventional water during their growth turn out to be free of pollutants. Unconventional water brings less heavy metals into the black soil than crops. The input and output quantities have only small effects on the heavy metal balance in the black soil. This paper provides a reference for the safety control and evaluation of unconventional agricultural utilization.

Impact Factors on Migration of Molybdenum(VI) from the Simulated Trade Effluent Using Membrane Chemical Reactor Combined with Carrier in the Mixed Renewal Solutions

Molybdenum is harmful and useful. The efficiency of molybdenum trade effluent treatment is low and it is difficult to extract and recycle. To solve this problem, a novel membrane chemical reactor with mixed organic-water solvent(MCR-OW) had been used for the investigation of impact factors on the migration characteristics of Mo(VI) in the simulated trade effluent. The novel MCR-OW contains three parts, such as feeding pool, reacting pool and renewal pool. Flat membrane of polyvinylidene fluoride(PVDF) membrane was used in the reacting pool, the mixed solutions of diesel and NaOH with N, N'-di(1-methyl-pentyl)-acetamide(N-503) as the carrier in the renewal pool and the simulated trade effluent with Mo(VI) as feeding solution. The influencing factors of pH and the ion strength in the feeding solutions, the volume ratio of diesel to NaOH solution and N-503 concentration in the renewal solutions were investigated for the testing of the migration efficiency of Mo(VI). It was found that the migration efficiency of Mo(VI) could reach 94.3% in 225 min, when the concentration of carrier(N-503) was 0.21 mol/L, the volume ratio of diesel to NaOH in the renewal pool was 4:3, pH in the feeding pool was 3.80 and the initial concentration of Mo(VI) was 2.50 × 10^-4 mol/L. Moreover, the stability and feasibility of MCR-OW were discussed according to Mo(VI) retention on the membrane and the reuse of the membrane.

Engineering Polyhistidine Tags on Surface Proteins of Acidithiobacillus ferrooxidans: Impact of Localization on the Binding and Recovery of Divalent Metal Cations

Metal processing using microorganisms has many advantages including the potential for reduced environmental impacts as compared to conventional technologies.Acidithiobacillus ferrooxidansis an iron- and sulfur-oxidizing chemolithoautotroph that is known to participate in metal bioleaching, and its metabolic capabilities have been exploited for industrial-scale copper and gold biomining. In addition to bioleaching, microorganisms could also be engineered for selective metal binding, enabling new opportunities for metal bioseparation and recovery. Here, we explored the ability of polyhistidine (polyHis) tags appended to two recombinantly expressed endogenous proteins to enhance the metal binding capacity of A. ferrooxidans. The genetically engineered cells achieved enhanced cobalt and copper binding capacities, and the Langmuir isotherm captures their interaction behavior with these divalent metals. Additionally, the cellular localization of the recombinant proteins correlated with kinetic modeling of the binding interactions, where the outer membrane-associated polyHis-tagged licanantase peptide bound the metals faster than the periplasmically expressed polyHis-tagged rusticyanin protein. The selectivity of the polyHis sequences for cobalt over copper from mixed metal solutions suggests potential utility in practical applications, and further engineering could be used to create metal-selective bioleaching microorganisms.