Ambroxol used as an expectorant in treating respiratory diseases was effectively prepared with a total yield of 62%, with o -toluidine as the feedstock via successive procedures of electrophilic bromination, acetylation, radical benzylic bromination, N -alkylation and hydrolysis processes. The addition of aqueous hydrogen peroxide could enhance the utilisation of liquid bromine in the electrophilic bromination of o -toluidine, avoiding the hazardous HBr generated as a by-product. In addition, liquid bromine promoted by MnO 2 was used efficiently for the radical benzylic bromination of N -acetyl- N -(2,4-dibromo-6-methylphenyl)acetamide under mild conditions.
Chao Zhu,Zarak Mahmood,Abdul Saboor Arshad,Jia Liu,Hongrui Ma
Wastewater treatment has become a major global issue due of undegradable pollutants. As toxic water pollutants , namely o-toluidine and p-toluidine are difficult to treat, this study uses the silicon rubber technology to treat them. A pair of modules having single tabular nonporous silicon rubber tube and HCl stripping solution were set up to extract o-toluidine and p-toluidine from high-saline wastewater. Reaction quotient ( Q C ) was calculated after every 12 h intervals to evaluate the equilibrium reaction. The effect of concentration, pH, temperature, ionic strength, and flow rate on the permeability (P) and removal efficiency ( η ) were investigated to illustrate the process parameters and mechanisms of recovery of both elements from wastewater. The results showed that the recovery efficiency was more than 96% with concentration of 2–10g/L. When pH of the extraction solution was 2 or less, the pollutant permeability efficiency was nearly 95%. Moreover, when the salting strength was over 10%, the recovery efficiency increased quickly to some extent. Permeability, which mainly influenced by membrane resistance and desorption rate, initially increased and then decreased when the water flow increased from 2 and 20 mL/min. Aging of silicon rubber tube was also studied with respect to salinity , temperature, and acidity. Acidity and temperature was found to have a significant effect on the tube, permeability increased with an increase in aging, and aging had a minor effect on the elastic properties of the silicon rubber tube. Absorption and diffusion of water in silicon rubber tubes decreased when salinity increased more than 10%, which increased separation of p-toluidine and water. Due to this, there is no need of desalination before membrane extraction in treatment of p-toluidine wastewater with high saline. Thus, this study demonstrates that membrane extraction is a highly energy-efficient process for the effective recovery of o-toluidine and p-toluidine from wastewater with high salinity.
The solubilization laws of pollutants in micelles and their separation efficiency are very important in the successfully efficient application of micellar enhanced ultrafiltration (MEUF). The solubilization behavior of o -toluidine (OT) and tricyclazole (TC) into sodium dodecyl sulfate (SDS) micelles in MEUF was studied using nonlinear equation sets for concentration analysis, which resolved the issue on the overlap of absorption spectra of multicomponent compounds restricting the application of conventional ultraviolet (UV) spectroscopic method. The solubilization isotherms for both pollutants could be best explained by the Langmuir-Freudlich model ( R 2 >0.99) followed by the modes of Langmuir and Freudlich, inferring the complexity of solubilization mechanism and solubilization advantage of monolayer over multilayer. The calculated thermodynamic parameters ( ΔG 0 , ΔH 0 and ΔS 0 ) indicated that this process was endothermic and spontaneous. The solubilization of OT and TC well followed the pseudo second-order and pseudo first-order kinetics, respectively. The separation and recovery of SDS solubilizing these two pollutants were also investigated through lowering solution temperature to 2 °C followed by centrifugation. The best recovery rate of about 66% for SDS was achieved containing 10 and 5% of each initial amount of OT and TC, respectively, at near-neutral solution pH value. The recovery of SDS could decrease to some extent under alkaline and acidic conditions.
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