Heterogeneous process with low mass transfer rate is limited in the treatment of large-volume Ni-containing wastewater. The homogeneous reaction provides a promising strategy to solve this problem, but phase transition process of Ni 2+ removal and its potential impact on activated sludge system are rarely explored. Herein, the Ni 2+ removal efficiency and process were firstly investigated in detail by using S-containing reagent with dithioamino groups. When the dosage of reagent concentration was controlled at 5–10:1(Ni), Ni 2+ can be rapidly and completely removed within 1 min. Additionally, other coexisting Cu 2+ , Co 2+ , Cd 2+ , and Pb 2+ could be synchronously removed with more reagent adding, while the typical organics (e.g., humic/citric acid) in water and high concentration of chemical oxygen demand (3800 mg L −1 ) in actual wastewater, exhibited negligible inhibition for Ni 2+ capture. The phase transition was visually investigated by charge coupled device camera and paticle size change. Experimental characterizations demonstrate that the dithioamino groups in capture reagent could efficiently chelate with Ni 2+ , which can be validated by the theoretical calculations. Vitally, the utilization of reagent cannot affect the nitrification activity of aerobic sludge system through short-term experiment and 29 months of operation while ensuring total Ni removal efficiency. These findings highlight an opportunity for using S-containing organic reagents to remove heavy metal ions from actual wastewater, especially in the application of the sewage treatment plant with bulky water.
There are plentiful ways to synthesize sulfidized nanoscale zerovalent iron (S-nZVI), and this study investigated the influence of sulfur reagents (Na 2 S, Na 2 S 2 O 3 , Na 2 S 2 O 4 ) and sulfidation sequence (co-sulfidation and post-sulfidation method) on the physicochemical properties, reactivity, and long-term performance of S-nZVI in simulated groundwater. The results suggested that the co-sulfidized nZVI (S-nZVI co ) has higher reactivity (∼2-fold) than S-nZVI post due to the stronger electron transfer capacity, deriving from the higher content of Fe 0 and reductive sulfur species. However, during aging, the reactivity of S-nZVI co would be lost more rapidly than S-nZVI post , due to the faster corrosion of Fe 0 and more oxidation of reductive sulfur species. S-nZVI post has the superior long-term performance with the degradation rate of trichloroethylene (TCE) remained at 30%∼60% even after 90 d of aging. Sulfur precursors can control the selectivity of S-nZVI by affecting the sulfur speciation on the particle surface. The proportion of reductive sulfur species on S-nZVI post synthesized by Na 2 S was higher than S-nZVI post synthesized by Na 2 S 2 O 3 or Na 2 S 2 O 4 , resulting in a higher selectivity of the former S-nZVI post than the latter S-nZVI post . In addition, sulfidation procedures and sulfur precursors did not affect the degradation pathway of TCE. Nevertheless, the degradation product distribution can be affected by the different physicochemical transformation of various types of S-nZVI with the aging time. These results indicated that sulfur reagents and sulfidation procedures have crucial effects on the reactivity and long-term performance of S-nZVI, which can be designed for the specific application scenarios.
危险品化学品经营许可证（带存储）