Physicochemical and environmental properties of arsenic sulfide sludge from copper and lead-zinc smelter

Physicochemical properties of arsenic sulfide sludge(ASS) from copper smelter(ASS-I) and lead-zinc smelter(ASS-II) were examined by XRD, Raman spectroscopy, SEM-EDS, TG-DTA, XPS and chemical phase analysis method. The toxicity characteristic leaching procedure(TCLP), Chinese standard leaching tests(CSLT), three-stage sequential extraction procedure(BCR) and batch leaching experiments(BLE) were used to investigate the environmental stability. The ASSs from different smelters had obviously different physicochemical and environmental properties. The phase composition and micrograph analysis indicate that ASS-I mainly consists of super refined flocculent particles including amorphous arsenic sulfide adhered with amorphous sulfur and that ASS-II mainly consists of amorphous arsenic sulfide. The valence state of arsenic in both sludges is trivalent, but the valence composition of sulfur is quite different. The ASSs have thermal instability properties. The results of TCLP and CSLT indicate that the concentrations of As and Pd in the leaching solution exceed the standard limits. More than 5% and 90% of arsenic are in the form of acid soluble and oxidizable fractions, respectively, which explains the high arsenic leaching toxicity and environmental activity of ASS. This research provides comprehensive information for the disposal of ASS from copper and lead-zinc smelter.

Process and mechanism of hydrothermal stabilization for arsenic sulfide sludge containing elemental sulfur

An optimized hydrothermal treatment was employed to stabilize the arsenic sulfide sludge(ASS). Under the optimal conditions(160 ℃, 2 h, liquid-to-solid(L/S) ratio of 1:1, and initial pH of 2), the leaching concentrations of As and Cd decreased from 504.0 and 12.0 mg/L to 1.23 and 0.03 mg/L of the treated ASS, respectively. The results indicate that the stabilization of the ASS was achieved through structure transformation from the particles into a bulk and the speciation transformation of As and Cd. Besides, sulfur in the ASS could significantly improve the stabilization property due to its melting and polymerization.

In vitro study on arsenic sulfide (realgar)-induced apoptosis of retinoic acid susceptible or resistant acute promyelocytic leukemia cell lines

Objective: To further understand the possible mechanisms of arsenic sulfide (realgar) in the treatment of acute promyelocytic leukemia (APL). Methods: All-trans retinoic acid (ATRA)-susceptible APL cell line (NB4 cells) and ATRA-resistant APL cell line (MR2 subclone) were used as models in vitro. At various times after incubated with various concentrations of realgar, NB4 and MR2 cells were observed by cell viability , cell proliferation and cell morphology; cell cycle and the expression of Annexin V were assayed by flow cytometry. Results: Cell viability and proliferation of NB4 and MR2 cells were inhibited after the treatment, to some extent, in a dose and time dependent manner. 177 - 711g/L of realgar treated NB4 and MR2 cell presented morphologically some features of apoptotic cells such as intact cell membrane, chromatin condensation and nuclear fragmentation, apoptosis body could be found by electron microscopy as well. Sub-Gl cells and cell cycle arrest were observed by flow cytometry. The proportion of Annexin V -FITC+/PI cells , which represent apoptotic cells, was up-regulated. Conclusion: Realgar could induce apoptosis of acute promyelocytic leukemia cell despite its susceptibility to retinoic acid in the way that may be different from retinoic acid.

Ferroptosis-inducing inorganic arsenic(II)sulfide nanocrystals enhance immune activation

Arsenic(II)sulfide is a stable inorganic arsenic compound with a different valence from arsenic trioxide,and has been widely applied to treat various diseases with low toxic side effects for a long time.However,its low solubility and complicated formulations restrict its further applications in modern medical industry.Meanwhile,as the tumour with the highest incidence rate among women,the low recurrence risk of breast cancer has been confirmed to be closely related to the high infiltration of immune cells.Herein,we synthesized and filtered novel biocompatible PEGylated arsenic(II)sulfide nanocrystals AsS@PEG with a size of 93.14±0.49 nm by the gel method,which displayed excellent anticancer and immune activation activity in breast cancer model.Proteomic analysis suggested that the AsS@PEG induce ferroptosis in cancer cells and further activate antitumour immune responses via B-cell lymphoma 9-like(BCL9L)protein inhibition.Furthermore,mechanism studies revealed notable glutathione peroxidase 4(GPX4)downregulation in cancer cells,dendritic cells(DCs)maturation and subsequent effector CD8^(+)T-cells production induced by the AsS@PEG in the tumour microenvironment.This study highlights biocompatible arsenic(II)sulfide nanocrystals that induce ferroptotic cell death and activate antitumour immune responses,providing insights into the path towards the immunotherapy assisted chemotherapy for breast cancer.