Yongkui Li,Xianjin Qi,Guohua Li,Xiaoxu Duan,Nina Yang
High-arsenic wastewater has long been considered a major threat to ecological balance and human health because of its strong toxicity and high mobility. Herein, an environmentally friendly process was proposed for As removal and fixation in the form of As-stabilized mineral, using Lead–Zinc smelting (LZS) slag as the in situ Fe donor, neutralizer, and crystal seed. The slag was dissolved in the wastewater and released Fe and Ca ions, while simultaneously increasing the pH value of the solution to help scorodite synthesis. The dissolved Ca 2+ ion preferentially reacted with SO 4 2− ion in the form of CaSO 4 ·2H 2 O precipitate as in situ “seeds” for As precipitation. The dissolved Fe(II) and As(III) ions were oxidized to Fe(III) and As(V) ions by H 2 O 2 , and later reacted with each other to generated amorphous ferric arsenate on the surface of CaSO 4 ·2H 2 O, and then evolved into scorodite crystals with high stability. With a Fe/As molar ratio of 2, a reaction temperature of 90 °C, and a reaction time of 12 h, 98.42% of As was effectively precipitated from the wastewater with an initial As concentration of 7530.00 mg/L. Moreover, the leached As concentration of the As-bearing precipitate in the TCLP test was 3.46 mg/L. The concentration of the residual As and heavy metals ions in the final filtrate was lower than local wastewater discharge standards, successfully realizing the treatment of smelting wastewater. In summary, a prospective process successfully shows a great potential for co-treatment of LZS wastewater and slag, which could advance the large-scale disposal of LZS plants.
Qiushi Zhang,Xing Cao,Shichang Sun,Weichen Yang,Lin Fang,Rui Ma,Chenghua Lin,Haowen Li
Lead-zinc slag (LZS) is a solid waste product that is rich in silicon and aluminum and has enormous resource potential for functional environmental functional geopolymer materials. Unfortunately, the solidification mechanism of heavy metals in geopolymers is still unclear, which is detrimental to the heavy metal solidification of LZS. In this study, we comprehensively studied and demonstrated the solidification mechanisms of Pb and Zn in geopolymers, based on the preparation of high-performance LZS-based geopolymers (compressive strength up to 89.3 MPa, and Pb and Zn solidification efficiency up to 93.1% and 90.0%, respectively). Thereafter, the solidification mechanism differences between Pb and Zn were explained by electronegativity and ion potential. Due to the ionic potential order of Zn 2+ > Pb 2+ > Na + , both Zn 2+ and Pb 2+ could exchange with Na + in the geopolymer. In addition, due to the electronegativity order of Pb > Si > Zn, Pb could attack the [SiO 4 ] structure and form covalent bonds in the Pb–O structure, while Zn did not (shown by Raman spectroscopy). As a result, Pb simultaneously solidified in the geopolymer through covalent bonding and ion exchange, while Zn was solidified mainly by ion exchange. Thus, this work provides new perspectives and ideas for the solidification mechanisms of heavy metals in geopolymers.
危险品化学品经营许可证（带存储）