Search

Atomized iron powder, carbonyl nickel powder, molybdenum powder, electrolytic copper powder, titanium powder and graphite powder were used as experimental materials; the titanium and graphite powders were added by an atomic ratio of Ti/C = 1:1 (the addition of Ti was 0 ∼ 4 wt%) to Fe-2Ni-0.5Mo-2Cu-0.3C powder, and the iron-based powder metallurgy materials reinforced by in situ-synthesized TiC particulates were prepared by a powder metallurgy technique. The results show that the microstructures of sintered samples are mainly pearlite, ferrite and bainite. The amount of pearlite increases with the increase of Ti content, whereas the ferrite and bainite decrease. TiC particles sized 0.3 µm distribute mainly near the grain boundary of pearlite. The apparent hardness of sintered samples increases, while the sintered density and flexural strength decrease with the increase of Ti content. The fracture morphology of the sintered materials is brittle type.

Proper disposal and resource recovery of spent batteries are crucial for environmental protection and sustainability. This study evaluated the adsorption performances of spent lithium iron phosphate (SLFP) and spent lithium manganate (SLMO) cathodes as adsorbents toward heavy metals in water. The effects of adsorption time, initial adsorbate concentrations, and co-existing ions on adsorption kinetics were examined. SLFP and SLMO demonstrated outstanding adsorption capacities for heavy metals that were higher than or comparable with other reported adsorbents. SLFP shows adsorption capacities of 44.28, 39.54, 25.63, and 27.34 mg g−1 for Cu2+, Pb2+, Cd2+ and Zn2+, respectively, SLMO achieved similar adsorption capacities (32.51, 31.83, 26.24 and 25.25 mg g−1, respectively). Among different adsorption kinetics model, the pseudo-second-order model described heavy metals adsorption kinetics best with R2 over 0.99, implying that chemisorption may be the predominant adsorption mechanism. The adsorption data at equilibrium well fitted the Langmuir isotherm model with R2 over 0.96, suggesting that the adsorption process could be endothermic. Cathode materials from of SLIBs may be recycled as adsorbents for heavy metal removal from water, which supports the “waste to treat waste” concept.

This study investigated the performance of an autohydrogenotrophic membrane biofilm reactor (MBfR) to remove nitrate from water with high sulfate concentrations. The results of simulated running showed that TN removal could be over than 98.8% with the maximum denitrification rate of 134.6 g N/m3 d under the conditions of the influent sulfate concentrations of 300 mg SO42−/l. The distribution ratio of H2 electron donor for nitrate and sulfate was 70.0 : 26.9 at the high influent loading ratio of sulfate/nitrate of 853.3 g SO42−/m3 d : 140.5 g N/m3 d, which indicated that denitrification bacteria (DB) were normally dominated to complete H2 electron with sulfate bacteria (SRB). The results of molecular microbiology analysis showed that the dominated DB were Rhodocyclus and Hydrogenophaga, and the dominated SRB was Desulfohalobium, under the high influent sulfate concentrations.

The performance of Cd, Ni, and Cu release from river sediment at different pH was investigated by a leaching test using deionised water and river water as leachants. Visual MINTEQ geochemical software was used to model the experimental results to predict heavy metal release from sediments. The distribution and speciation of heavy metals in the sediments after leaching test were analyzed by Tessier sequential extraction. Leaching test results showed that the release amounts of Cd, Ni, and Cu are in the range of 10.2–27.3 mg·kg−1, 80.5–140.1 mg·kg−1, and 6.1–30.8 mg·kg−1, respectively, with deionised water as leachant at different pH. As far as the river water was used as the leaching solution in the test, the results show similar metal leaching contents and tendencies to that of the deionised water as leaching solution. The results of Tessier sequential extraction indicate that Cd of residual fraction easily forms obvious precipitate under the acidic condition, especially in the range of pH 0–4 with the residual of Cd over 50% of the total Cd in the sediment. The exchangeable content of Ni decreases with the increase of pH under the range of 0–5. The Fe-Mn oxide fraction of Cu in the sediments changes significantly from pH 0 to pH 9. Based on the effect of pH on the leaching of Cd, Ni, and Cu from the polluted sediment in the tests, more accurate information could be obtained to assess the risk related to metal release from sediments once it is exposed to the changed acid/alkali water conditions.