Hao Peng,Zonghui Qin,Guixuan Jin,Jingjing Wang,Jielin Qin,Lihua Ao,Bing Li
In this paper, tartaric acid (C4H6O6) was used as a reductant to treat chromium (VI)-containing solution. Several independent experimental parameters, including reaction temperature, concentration of H2SO4, concentration of C4H6O6and reaction time, on the reduction process were studied. The results showed that 100% of the Cr (VI) could be reduced by C4H6O6in a strong acidic environment under a high reaction temperature. All of the experimental parameters showed positive effects on the reduction process and followed the order [H2SO4] > [C4H6O6] > reaction temperature > reaction time. A higher concentration of tartaric acid and higher reaction temperature could facilitate the reduction process and reduce reaction time.
It is critical for reactor design and process safety to determine the reaction kinetics for toluene nitration. Herein, a continuous-flow platform based on capillary microreactors was established. First, reaction regimes for toluene nitration and its consecutive side reaction (MNT (mononitrotoluene) nitration) were identified. On this basis, the influence of process parameters on conversion of toluene, selectivity of MNT and DNT (dinitrotoluene) and their isomer distribution were meticulously examined, including molar ratio of reactants, sulfuric acid strength, reaction temperature, and residence time. Subsequently, reaction kinetic models coupled with mass transfer were developed, allowing the simultaneous kinetic determination for toluene nitration and MNT nitration. It was found that the logarithm of the observed kinetic constant is proportional to the sulfuric acid strength. The kinetic parameters under 72.7 to 80.1 wt% sulfuric acid strengths were obtained. The outcomes provide a basis for process intensification and optimization of toluene nitration as well as other similar aromatics.
Electrodialysis (ED) was widely use for sulfuric acid (H 2 SO 4 ) recovery. However, challenges such as proton leakage during ED processes and the presence of large amounts of organic solvents in the wastewater have limited the recovered acid concentration to less than 30 wt% and shortened membrane lifespan. In this study, we prepared a series of anion exchange membranes (AEMs) using 3-aminopropyltrimethoxysilane (APTMS) and phenyltriethoxysilane (phTES) as cross-linking agents aimed at concentrating H 2 SO 4 through the ED process. As the content of bis-siloxane crosslinkers increased, the ion exchange capacity (IEC) of the membranes decreased from 1.86 to 1.27 mmol g −1 , resulting in lower water flux and membrane conductivity. However, the increased crosslinker content significantly enhanced membrane hydrophobicity, thereby improving its acid-blocking properties. During ED operations at a current density of 10 mA cm −2 , the BPPO-10APTMS-10phTES membrane achieved a H + concentration of 2.15 mol/L (from an initial concentration of 1.00 mol/L), outperforming AEMs without cross-linking structure. Additionally, the BPPO-xAPTMS-xphTES membranes (x = 5, 10, and 15) exhibited strong resistance to organic solvents. This research offers valuable theoretical guidance for developing AEMs with enhanced acid concentration capabilities and solvent resistance.
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