Wang Gangan, Chen Chaoyi, Li Junqi, Lan Yuanpei, Lin Xin, Chen Jiahang
School of Materials and Metallurgy, Guizhou University, Guiyang 550025, China.
Guizhou Province Dual Carbon and New Energy Technology Innovation and Development Research Institute, Guiyang 550025, China.
Molecules. 2024 Jun 4;29(11):2665. doi: 10.3390/molecules29112665.
The discharge of lead and cadmium wastewater, along with the pollution caused by phosphogypsum, represents a particularly urgent environmental issue. This study employed a straightforward hydrothermal method to convert phosphogypsum into porous calcium silicate hydrate (P-CSH), which was then used to remove and recover Pb(II) and Cd(II) from wastewater. The adsorption capacities of P-CSH for Pb(II) and Cd(II) were notably high at 989.3 mg/g and 290.3 mg/g, respectively. The adsorption processes adhered to the pseudo-second-order kinetics model and the Langmuir isotherm model. Due to identical adsorption sites on P-CSH for both Pb(II) and Cd(II), competitive interaction occurred when both ions were present simultaneously. Additionally, the adsorption efficacy was minimally impacted by the presence of common coexisting cations in wastewater. The dominant mechanisms for removing Pb(II) and Cd(II) via P-CSH were chemical precipitation and surface complexation. Moreover, the adsorbed heavy metals were efficiently separated and reclaimed from the wastewater through a stepwise desorption process. The primary components of the residue from stepwise desorption were quartz and amorphous SiO. Following dissolution via pressurized alkaline leaching, this residue could be recycled for synthesizing P-CSH. This research offered a new strategy for the resourceful use of phosphogypsum and heavy metal wastewater.
铅镉废水的排放以及磷石膏造成的污染是一个尤为紧迫的环境问题。本研究采用一种简单的水热法将磷石膏转化为多孔硅酸钙水合物（P-CSH），然后用其从废水中去除并回收Pb(II)和Cd(II)。P-CSH对Pb(II)和Cd(II)的吸附容量分别高达989.3 mg/g和290.3 mg/g。吸附过程符合准二级动力学模型和朗缪尔等温线模型。由于P-CSH对Pb(II)和Cd(II)具有相同的吸附位点，当两种离子同时存在时会发生竞争作用。此外，废水中常见共存阳离子的存在对吸附效果的影响极小。通过P-CSH去除Pb(II)和Cd(II)的主要机制是化学沉淀和表面络合。而且，通过分步解吸过程可将吸附的重金属从废水中有效分离并回收。分步解吸残渣的主要成分是石英和无定形SiO。经加压碱浸溶解后，该残渣可循环用于合成P-CSH。本研究为磷石膏和重金属废水的资源化利用提供了一种新策略。
