A copper-organic framework as scavenger towards organic dyes pollutants via physical adsorption and visible-light photodegradation

Application of QSAR for investigation on coagulation mechanisms of textile wastewater

Coagulation is an effective preliminary treatment process for textile wastewater. In order to evaluate the effectiveness of the coagulation process, we performed quantitative structure activity relationship (QSAR) analyses with total organic carbon (TOC) removal rates (R_exp) as an index by three different coagulants (AlCl₃, FeCl₃, and MgCl₂). The experimental results showed that the average R_exp of the three coagulants was 39.12% ± 2.60%, 51.60% ± 2.88%, and 49.95% ± 3.17%. Subsequently, 42 molecular descriptors of dye molecules were calculated by quantitative calculation softwares Gaussian 09, Material Studio 7.0, and Multiwfn 3.7, and then QSAR models were constructed by a multiple linear regression (MLR) method for the three coagulation systems. The developed QSAR models demonstrated excellent stability, robustness, and predictability with values of R² = 0.7677, 0.8015, and 0.7035, Q²_INT = 0.6067, 0.7026, and 0.5898, Q²_EXT = 0.5505, 0.5076, and 0.5697, respectively. Based on the analysis of quantum parameters, the coagulation mechanism for AlCl₃, FeCl₃ is primarily electrostatic adsorption as well as hydrogen bonding, while MgCl₂ coagulates dyes mainly by electrostatic adsorption. This study provides an assessment of the removal rules and a feasible method for predicting dye removal rates in AlCl₃, FeCl₃, and MgCl₂ coagulation process.

Effective degradation of Orange G and Rhodamine B by alkali-activated hydrogen peroxide: roles of HO2- and O2·

Advanced oxidation processes offer effective solutions in treating wastewater from various industries. The process of alkali-activated hydrogen peroxide (H₂O₂) was superior for the treatment of alkaline dye wastewater because no additional reagents were required except H₂O₂. However, an important and interesting phenomenon had been observed that the primary reactive species were found different for degrading organic pollutants with the process of alkali-activated H₂O₂. Azo dye of Orange G (OG) and triphenylmethane dye of Rhodamine B (RhB) were chosen as the target organic pollutants. The influences of various parameters on OG and RhB degradation by alkali-activated H₂O₂ were evaluated. Furthermore, different scavengers, including ascorbic acid, methanol, t-butanol, isopropyl alcohol, furfuryl alcohol, and nitro blue tetrazolium, have been tested to identify the active species involved in dye degradation, and it was found that O₂^·- was mainly responsible for degrading OG, while HO₂^- anion was the primary oxidant for degrading RhB.