A novel intensification technology–microwave reactive distillation (MRD) process was developed by coupling the microwave irradiation and reactive distillation (RD) process to break through the limitations of the RD process, such as low esterification reaction rate. The batch MRD process and RD process for acetic acid and ethanol esterification were compared by using a laboratory-scale RD packed column with strong acidic ion-exchange resin as catalyst. The effects of reflux ratio, feed flow rate, microwave power, and reboiler heating power were investigated. The results showed that, with the same total energy consumption, MRD needed less time than RD to obtain 70% overhead EtAc content. Compared with the RD process, the instantaneous improvement of ethyl acetate content achieved by MRD was up to 6.9% under same reflux ratio, and 6.7% under same acetic acid feed flow rate. The variation trend of experimental results matched that of the numerical simulation results.

•A large scale subcritical ethanol extraction was conducted to extract flavonoids.•An optimal condition of extraction was proposed.•The extraction process was energy-saving.•The extracts showed strong antioxidant ability.•HPLC–MS analysis was performed to identify the flavonoids.A large-scale process to extract flavonoids from Moringa oleifera leaf by subcritical ethanol was developed and HPLC–MS analysis was conducted to qualitatively identify the compounds in the extracts. To optimize the effects of process parameters on the yield of flavonoids, a Box-Behnken design combined with response surface methodology was conducted in the present work. The results indicated that the highest extraction yield of flavonoids by subcritical ethanol extraction could reach 2.60% using 70% ethanol at 126.6 °C for 2.05 h extraction. Under the optimized conditions, flavonoids yield was substantially improved by 26.7% compared with the traditional ethanol reflux method while the extraction time was only 2 h, and obvious energy saving was observed. FRAP and DPPH assays showed that the extracts had strong antioxidant and free radical scavenging activities.

•Solubility data of wedelolactone in a binary system of ethanol and water from 278.15 to 323.15 K were measured.•The solubility varies with the composition of the solvent and temperature.•The measured data were regressed with modified Apelblat, Wilson, NRTL and CNIBS models.•The thermodynamic properties of dissolution were calculated using van’t Hoff equation and Gibbs equation.•The dissolution of wedelolactone in a binary system of ethanol and water is endothermic and no-spontaneous process.Experimental solubility data of wedelolactone in a binary system of ethanol and water from 278.15 K to 323.15 K were measured using a thermostatted reactor by static method and HPLC analysis. The effects of binary solvents composition and temperature on the solubility were discussed and it was found that wedelolactone solubility in (water + ethanol) mixed solvents presented a monotonic effect in the studied region. The measured data were regressed by the modified Apelblat equation, Wilson model, nonrandom two-liquid (NRTL) model and the binary solvent (CNIBS)/Redlich–Kister model, and the maximum ∑(%D) values were 0.75, 1.90, 4.34 and 0.38, respectively. The correlation results showed that calculated values by the four models agree well with the experimental data. Using the experimentally measured solubility values, the thermodynamic properties of dissolution of the wedelolactone, including Gibbs energy change (ΔGd), molar enthalpy change (ΔHd) and molar entropy change (ΔSd) of dissolution, were calculated. The values of the standard molar Gibbs energy change and standard enthalpy molar change of solution were both positive, which indicated that the dissolution of wedelolactone in the binary system of ethanol and water was endothermic and no-spontaneous process.

•Isobaric VLE data were reported for the binary systems at 0.5, 1.0 and 1.4 kPa.•Thermodynamic consistency of the experimental data was checked both with the Wisniak consistency test and Van Ness test.•The experimental VLE data were regressed with NRTL and Wilson models.•The experimental VLE data were predicted by UNIFAC and Dortmund (modified UNIFAC) models.•All the four models indicate a reasonable agreement between experimental and calculated data for the VLE data.Isobaric vapor–liquid equilibrium (VLE) data for the binary system of methyl myristate + methyl palmitate at 0.5, 1.0 and 1.4 kPa were measured by a VLE modified Othmer still. The esters used in this paper are the major components of biodiesel. The experimental data in the vaccum conditions passed the Wisniak consistency test and point consistency test of Van Ness test, which ensure the reliability of experimental data. Furthermore, these VLE data were correlated with Nonrandom two-liquid (NRTL) activity coefficient model and Wilson model, and predicted by UNIFAC and Dortmund (modified UNIFAC) models. The results indicate that the calculated values of these four models agree well with the experimental data.

An efficient microwave-assisted extraction technique was used to extract wedelolactone from Eclipta alba. To optimize the effects of the microwave-assisted extraction (MAE) processing parameters on the yield of wedelolactone, a response surface methodology with a central composite rotatable design was employed. Four independent variables were investigated: microwave power, ethanol concentration, extraction time and the solvent-to-solid ratio. The optimum conditions were: microwave power, 208W; ethanol concentration, 90%; extraction time, 26.5min; and solvent-tosolid ratio, 33mL·g−1. Under the optimal conditions, the extraction yield of wedelolactone was (82.67±0.16)%, which is in close agreement with the value predicted by the statistical model. MAE was also compared to other conventional methods, including ultrasonic assisted extraction, extraction at room temperature and heat reflux extraction. MAE has distinct advantages for the extraction of wedelolactone in terms of both time and efficiency. Therefore, MAE is a reliable method for the extraction of wedelolactone from Eclipta alba.

Isobaric vapor–liquid equilibrium (VLE) data for the system (ethyl myristate + ethyl palmitate) were measured at 0.5, 1.0 and 1.5 kPa with a VLE modified Othmer still. The esters used in this study are the major components of biodiesel. Thermodynamic consistency of the experimental data was checked both with the Herington consistency test and point consistency test of Van Ness Test, which ensure the reliability of experimental data. Furthermore, the experimental VLE data were regressed with Nonrandom Two-Liquid (NRTL) activity coefficient model and predicted by UNIFAC and Dortmund (modified UNIFAC) models. The results show that the calculated values of the vapor-phase mole fraction and boiling temperature by NRTL, UNIFAC models and Dortmund model agree well with the experimental data.

Isobaric vapor–liquid equilibrium (VLE) data of the mixture of methyl palmitate and methyl stearate at 0.1 kPa, 1 kPa, 5 kPa, and 10 kPa were measured with a modified Othmer still. Methyl palmitate and methyl stearate were the major components of the biodiesel. The experimental results were correlated with Wilson and nonrandom two-liquid (NRTL) activity coefficient models and were compared with a group contribution model (UNIFAC). The binary interaction parameters of the Wilson and NRTL models were fitted into the experimental data which were obtained at different pressures. The UNIFAC model did not predict the VLE for methyl palmitate and methyl stearate at reduced pressures well. The Wilson and NRTL models could well correlate with the experimental data at 1 kPa, 5 kPa, and 10 kPa. However, for the lower pressure 0.1 kPa, the Wilson model and NRTL model had worse correlatations with our experimental data than the higher pressures. These models could develop VLE calculations of the mixtures and provide guidelines for the separation of components by vacuum distillation.

•The VLE data for binary system methyl caprylate and methyl caprate were measured.•The Wilson, NRTL and UNIFAC models were used to reproduce the experimental values.•The COSMO-SAC model was applied to predict the VLE of the binary system.•All four models provided great reproductions, especially the NRTL model.The isobaric vapor-liquid equilibrium data for the binary system methyl caprylate (1) + methyl caprate (2) at 2, 6 and 10 kPa were measured with a modified Othmer still. All the experimental data were verified to be thermodynamically consistent according to the Van Ness test method. Two activity coefficient models (Wilson and NRTL) were applied to regress the experimental values. Furthermore, the group contribution method (UNIFAC) and the COSMO-SAC model were also employed to predict vapor-liquid equilibrium data. The four models reproduced the experimental values very well, while the NRTL model provided a slightly better result than the other three models, with the root mean square deviations of temperature and vapor-phase mole fraction less than 0.36 K and 0.0042, respectively.

•Low-level chamber pressure did not exert significant effect on zinc removal.•Central composite design selected the process variables with significant effects.•The zinc in metallic mixture could be efficiently removed by vacuum distillation.•The Blake-Kozeny–Burke-Plummer equation was introduced into mass transfer equation.•A layer model was established to elucidate the mechanism of zinc removal.A layer model was established to elucidate the mechanism of zinc removal from the metallic mixture of waste printed circuit boards by vacuum distillation. The removal process was optimized by response surface methodology, and the optimum operating conditions were the chamber pressure of 0.1 Pa, heating temperature of 923 K, heating time of 60.0 min, particle size of 70 mesh (0.212 mm) and initial mass of 5.25 g. Evaporation efficiency of zinc, the response variable, was 99.79%, which indicates that the zinc can be efficiently removed. Based on the experimental results, a mathematical model, which bears on layer structure, evaporation, mass transfer and condensation, interprets the mechanism of the variable effects. Especially, in order to reveal blocking effect on the zinc removal, the Blake-Kozeny–Burke-Plummer equation was introduced into the mass transfer process. The layer model can be applied to a wider range of metal removal by vacuum distillation.

•A novel way for synthesizing water-soluble thiourea-formaldehyde resin was proposed.•The resin decreased effectively the leaching concentrations of Cr, Pb and Cd.•Melamine can effectively decrease the content of free formaldehyde in the resin.•The structure was characterized by elemental analysis and FTIR spectra.Because of the high concentrations of heavy metals, municipal solid waste incineration (MSWI) fly ash is classified as a hazardous waste, which need to be treated to avoid damaging the environment. A novel water-soluble thiourea-formaldehyde (WTF) resin was synthesized by two step reactions (hydroxymethylation reaction and condensation reaction) in the laboratory. Synthetic conditions, removal of free formaldehyde in the resin and the ability of immobilization heavy metals in the MSWI fly ash were studied. The possible molecular structure of the resin was also discussed by elemental analysis and FTIR spectra. Experimental results showed that the synthesis conditions of WTF resin were the formaldehyde/thiourea (T/F) mole ratio of 2.5:1, hydroxymethylation at pH 7.0–8.0 and 60 °C for 30min, and condensation of at pH 4.5–5.0 and 80 °C. In addition, the end point of condensation reaction was measured by turbidity point method. The result of elemental analysis and FTIR spectra indicated that thiourea functional group in the WTF resin chelated the heavy metal ions. Melamine can efficiently reduce the free formaldehyde content in the resin from 8.5% to 2%. The leaching test showed that the immobilization rates of Cr, Pb and Cd were 96.5%, 92.0% and 85.8%, respectively. Leaching concentrations of Cr, Pb and Cd in the treated fly ash were decreased to 0.08 mg/L, 2.44 mg/L and 0.23 mg/L, respectively. The MSWI fly ash treated by WTF resin has no harm to the environment.Download high-res image (68KB)Download full-size image