Solidification/stabilization of highly toxic arsenic-alkali residue by MSWI fly ash-based cementitious material containing Friedel's salt: Efficiency and mechanism.

Arsenic-alkali residue (AAR) and MSWI fly ash (MFA) are hazardous wastes, which still lack effective treatment methods. In this study, a novel solidification/stabilization (S/S) method for AAR with MFA-based cementitious material (MFA-CM) containing Friedel's salt was proposed. The efficiency and mechanism of S/S was mainly focused. Abundant Friedel's salt as well as a few C-S-H gel and ettringite (AFt) were found as hydration products of MFA-CM. 12% of AAR was well solidified/stabilized by MFA-CM, accompanied by As leaching concentration reducing from 10,687 mg/L to less than 5 mg/L. In order to investigate S/S mechanism of As, removal mechanism of As during co-precipitation synthesis of Friedel's salt was studied. During co-precipitation process, As was successively removed by formation of calcium arsenate precipitates, formation of As-Friedel's salt (replacement of Cl- by AsO43-), and adsorption of Friedel's salt. The S/S mechanism of As by MFA-CM was found to be similar to the removal mechanism of As during co-precipitation. With the prolonging of curing time, As was mainly solidified/stabilized by formation of calcium arsenate precipitates and As-Friedel's salt, and adsorption of Friedel's salt. Thus, this study provides a novel harmless treatment method for highly toxic arsenic-containing wastes by "treating the wastes with wastes".

Suicidal and self-harm ideation among Chinese hospital staff during the COVID-19 pandemic: Prevalence and correlates.

The COVID-19 pandemic put global medical systems under massive pressure for its uncertainty, severity, and persistence. For detecting the prevalence of suicidal and self-harm ideation (SSI) and its related risk factors among hospital staff during the COVID-19 pandemic, this cross-sectional study collected the sociodemographic data, epidemic-related information, the psychological status and need, and perceived stress and support from 11507 staff in 46 hospitals by an online survey from February 14 to March 2, 2020. The prevalence of SSI was 6.47%. Hospital staff with SSI had high family members or relatives infected number and the self-rated probability of infection. Additionally, they had more perceived stress, psychological need, and psychological impact. On the contrary, hospital staff without SSI reported high self-rated health, willingness to work in a COVID-19 ward, confidence in defeating COVID-19, and perceived support. Furthermore, they reported better marital or family relationship, longer sleep hours, and shorter work hours. The infection of family members or relatives, poor marital status, poor self-rated health, the current need for psychological intervention, perceived high stress, perceived low support, depression, and anxiety were independent factors to SSI. A systematic psychological intervention strategy during a public health crisis was needed for the hospital staff's mental well-being.

Cotreatment of MSWI Fly Ash and Granulated Lead Smelting Slag Using a Geopolymer System.

Municipal solid waste incineration fly ash (MSWI FA) and granulated lead smelting slag (GLSS) are toxic industrial wastes. In the present study, granulated lead smelting slag (GLSS) was pretreated as a geopolymer precursor through the high-energy ball milling activation process, which could be used as a geopolymeric solidification/stabilization (S/S) reagent for MSWI FA. The S/S process has been estimated through the physical properties and heavy metals leachability of the S/S matrices. The results show that the compressive strength of the geopolymer matrix reaches 15.32 MPa after curing for 28 days under the best parameters, and the physical properties meet the requirement of MU10 grade fly ash brick. In addition, the toxicity characteristic leaching procedure (TCLP) test results show that arsenic and heavy metals are immobilized effectively in the geopolymer matrix, and their concentrations in the leachate are far below the US EPA TCLP limits. The hydration products of the geopolymer binder are characterized by X-ray diffraction and Fourier transform infrared methods. The results show that the geopolymer gel and Friedel's salt are the main hydration products. The S/S mechanism of the arsenic and heavy metals in the geopolymer matrix mainly involves physical encapsulation of the geopolymer gel, geopolymer adsorption and ion exchange of Friedel's salt.