School of Environmental Science and Engineering, Shaanxi University of Science & Technology, Xi'an, 710021, PR China; School of Chemical Engineering, Shenmu Vocational & Technical College, Shenmu, 719300, PR China.
School of Environmental Science and Engineering, Shaanxi University of Science & Technology, Xi'an, 710021, PR China.
Environ Res. 2020 Apr;183:109159. doi: 10.1016/j.envres.2020.109159. Epub 2020 Jan 21.
As a hazardous waste, the disposal of chromium enriched tannery sludge has attracted increasing public concern due to its potential adverse risks towards the environment. And incineration is considered to be an effective method to stabilize heavy metals, like Cr, in solid phase during tannery sludge treatment. In this study, real chromium enriched tannery sludge without pre-treatment was incinerated at 300°C-1200 °C under air atmosphere to investigate the transformation of chromium speciation. Here detailed thermal behavior, phase transformation and chromium speciation were characterized by TG-DSC, XRD and XPS, respectively. Experimental results show that content of Cr(VI) increases gradually with the increase of temperature from 300 °C to 500 °C and reaches a maximal level of 46% total Cr at 500 °C, with different Cr(VI) species of CaCrO, MgCrO and CrO. However, the content of Cr(VI) decreases gradually with the further increase of temperature, with only about 5% Cr(VI) at high temperature of 1200 °C, due to formation of Cr(III) species of CrO crystallite and MgCrO spinel. Besides, a growing number of hexagonally shaped flake-like crystallite CrO can be discovered from characterization results of XRD and SEM. Finally, the reduction of CaCrO to CrO in the presence of SiO is thermodynamically feasible over 700 °C, indicating possible transformation of Cr(VI) to Cr(III) through controlled incineration temperature.
作为一种危险废物，由于富含铬的制革污泥对环境具有潜在的不利风险，其处理已引起越来越多的公众关注。焚烧被认为是一种有效的方法，可以在制革污泥处理过程中将重金属（如 Cr）稳定在固相中。在本研究中，未经预处理的实际富含铬的制革污泥在空气气氛下于 300°C-1200°C 下焚烧，以研究铬形态的转化。详细的热行为、相变和铬形态通过 TG-DSC、XRD 和 XPS 分别进行了表征。实验结果表明，Cr(VI)的含量随着温度从 300°C 升高到 500°C 而逐渐增加，在 500°C 时达到总 Cr 的最大水平 46%，其中含有不同的 Cr(VI)物种，如 CaCrO、MgCrO 和 CrO。然而，随着温度的进一步升高，Cr(VI)的含量逐渐降低，在高温 1200°C 时只有约 5%的 Cr(VI)，这是由于 Cr(III)物种的 CrO 微晶和 MgCrO 尖晶石的形成。此外，从 XRD 和 SEM 的表征结果可以发现，越来越多的六方片状微晶 CrO 可以被发现。最后，在存在 SiO 的情况下，CaCrO 还原为 CrO 的反应在 700°C 以上是热力学可行的，这表明通过控制焚烧温度，Cr(VI)可能转化为 Cr(III)。
