A novel process integrating vacuum distillation with atmospheric chlorination reaction for flexible production of tetrachloroethane and pentachloroethane

In this paper, we developed a novel process integrating vacuum distillation with atmospheric chlorination reaction(VD-ACR) to realize the flexible production of tetrachloroethane(TeCA) and pentachloroethane(PCA)from 1,2-dichloroethane(DCA). During the simulation, the distillation column and reactors were operated for separation and chlorination respectively under variable pressures and temperatures. It is interesting to note that VD-ACR processes producing pure TeCA or PCA can exhibit the similar configuration parameters after optimization, which enables the flexible production of TeCA and PCA with different molar ratios via changing operating parameters. The molar ratio of TeC A/PCA can be fine-tuned within the range of 0.9:0.1-0.1:0.9 through adjusting the amount of chlorine pumped into side reactors, giving rise to the increase of the heat duty of reboiler by five times. A pilot-scale experiment was then operated based-upon this VD-ACR process and the result matched well with the simulation. Therefore, the VD-ACR model presented in this study will be beneficial for the industrial-scale flexible production of TeCA and PCA from DCA.

Formation of disinfection byproducts from accumulated soluble products of oleaginous microalga after chlorination

When microalgae are simultaneously applied for wastewater treatment and lipid production, soluble algal products （SAP） should be paid much attention, as they are important precursors for formation of disinfection byproducts （DBPs）, which have potential risks for human health. Chlorella sp. HQ is an oleaginous microalga that can generate SAP during growth, especially in the exponential phase. This study investigated the contribution of SAP from Chlorella sp. HQ to DBP formation after chlorination.The predominant DBP precursors from SAP were identified with the 3D excitation-emission matrix fluorescence. After chlorination, a significant reduction was observed in the fluorescence intensity of five specific fluorescence regions, particularly aromatic proteins and soluble microbial by-product-like regions, accompanied with slight shifting of the peak. The produced DBPs were demonstrated to include trihalomethanes and haloacetic acids. As the algal cultivation time was extended in wastewater, the accumulated SAP strengthened the formation of DBPs. The trend for DBP formation was as follows： chloroform〉dichloroacetic acid〉trichloroacetic acid.

DBP formation from degradation of DEET and ibuprofen by UV/chlorine process and subsequent post-chlorination

The formation of disinfection by-products（DBPs） from the degradation of N,N-diethyl-3-methyl benzoyl amide（DEET） and ibuprofen（IBP） by the ultraviolet irradiation（UV）/chlorine process and subsequent post-chlorination was investigated and compared with the UV/H_2O_2 process.The pseudo first-order rate constants of the degradation of DEET and IBP by the UV/chlorine process were 2 and 3.1 times higher than those by the UV/H_2O_2 process, respectively, under the tested conditions. This was due to the significant contributions of both reactive chlorine species U（RCS） and hydroxyl radicals（HO） in the UV/chlorine process. Trichloromethane, 1,1,1-trichloro-2-propanone and dichloroacetic acid were the major known DBPs formed after 90% of both DEET and IBP that were degraded by the UV/chlorine process. Their yields increased by over 50%after subsequent 1-day post-chlorination. The detected DBPs after the degradation of DEET and IBP comprised 13.5% and 19.8% of total organic chlorine（TOCl）, respectively, and the proportions increased to 19.8% and 33.9% after subsequent chlorination, respectively. In comparison to the UV/H_2O_2 process accompanied with post-chlorination, the formation of DBPs and TOCl in the UV/chlorine process together with post-chlorination was 5%–63% higher,Ulikely due to the generation of more DBP precursors from the attack of RCS, in addition to HO.