Lab-scale Bubbling Reactor Research Articles

Simultaneous treatment of toluene-containing gas waste and industrial wastewater by the Fenton process

This study reports a new perspective for the simultaneous oxidation of a volatile organic compound (VOC) – a toluene gas stream – and a real industrial liquid effluent by the Fenton's process; for that, a lab-scale bubbling reactor, operating in semi-continuous mode, was used. A parametric study was carried out to evaluate the effect of the aqueous matrix (water vs. real effluent), catalyst species nature (Fe2+ vs. Fe3+), concentration of organic matter in the liquid, and inlet toluene concentration in the gas phase. Their effects in the simultaneous gas-liquid treatment were assessed in terms of the toluene removal (from the gas stream) and wastewater mineralization (removal of dissolved organic carbon - DOC). The presence of organic matter in the liquid phase decreased toluene absorption. However, the simultaneous oxidation in the liquid phase extended the period of absorption until its saturation (and inherently the amount of toluene transferred) while still oxidizing 25% of the organic matter present in the industrial effluent. The application of the Fenton-like (H2O2 + Fe3+) process yielded a slightly reduced toluene transfer as compared to the Fenton one (H2O2 + Fe2+) – ca. 10%, although the overall mineralization has been similar. As expected, increasing the inlet toluene concentration reduces the process duration until liquid saturation, at the same time that a higher accumulation of by-products in the liquid due to oxidation was observed. Finally, a sequential treatment approach was performed, wherein liquid oxidation follows the previous simultaneous gas-liquid treatment, representing a strategy for long term operation, providing an opportunity for further VOC abatement in subsequent cycles. The main compounds resulting from oxidation remaining in the liquid phase after each stage were identified, allowing to close the carbon balance by ca. 80%.

CO2 capture and sequestration by sodium humate and Ca(OH)2 from carbide slag

A new method of carbon capture and sequestration (CCS) by sodium humate (HA–Na) and Ca(OH)2 from carbide slag (CS) solution was proposed. The effects of various operating parameters, such as the additive amount of HA–Na, pH, temperature, gas flow rate, CO2 inlet concentration, and stirring rate on both the Ca ion concentration and Ca conversion rate were investigated in a lab-scale bubbling reactor. The synergistic mechanism of HA–Na and Ca(OH)2 from CS on CCS is also put forward and demonstrated. The experimental results indicate that HA–Na may improve significantly the CCS capability of CS since the Ca conversion rate of CS is increased 10% by HA–Na additive. The pH is a key factor for the CO2 absorption process and HA–Na may lower the rate of pH decrease of Ca(OH)2 solution. The increasing temperature, stirring rate, and CO2 inlet concentration are favorable to CO2 capture, as well as low gas flow rate. Ca(OH)2 from CS mixed with HA–Na solution shows good performance in CO2 uptake, and the Ca conversion rate reaches 99% with 100 mL of Ca(OH)2 (1.5 g/L) solution mixed with 0.1 g HA–Na at 40 °C, a gas flow rate of 0.1 L/min, and an inlet CO2 concentration of 100% at ambient pressure. Moreover, calcite CaCO3 is is identified as the main product of CO2 capture by X-ray diffraction and scanning electron microscopy analysis.

Study on a Novel Oxidation Process for Removing Arsenic from Flue Gas

The experiments of arsenic removal from flue gas were investigated at a lab-scale bubbling reactor with H2O2 solution to develop a novel oxidation process. The effects of various experimental parameters, such as H2O2 concentration, initial solution pH, reaction temperature, and flue gas components (O2, CO2, SO2, and NO) were systematically investigated, and the average removal efficiency was found to be 92.6%, under the obtained optimal conditions, in which H2O2 concentration was 0.2 mol/L, solution pH was 5.0, and reaction temperature was 50 °C. Meanwhile, the mechanism of the reaction was proposed based on characterizations of the removed products by high performance liquid chromatography coupled to hydride generation atomic fluorescence spectrometry, atomic fluorescence spectrometry as well as a review of the literature.

Influence of operating parameters on performance of SO2 absorption in fulvic acid solution

A novel process of flue gas desulfurization by aqueous fulvic acid (FA) solution with acid-base buffering capacity was developed. Experiments were carried out to investigate the influence of operating parameters such as the FA concentration, pH, temperature, gas flow rate, fly ash, O2, SO2 inlet concentration, CO2 and NO2 on SO2 absorption efficiency and Duration Time of High Efficiency (DTHE, the time of the SO2 absorption efficiency above 95%) in a lab-scale bubbling reactor. The results show high FA concentration has more absorption capacity for SO2, and the optimum concentration of FA solution is 0.08gmL−1, at which point the absorption efficiency is above 98%. The inlet SO2 concentration has little influence on absorption efficiency, but DTHE reduces with increasing inlet SO2 concentration. O2 has a little effect on absorption efficiency. The SO2 absorption efficiency is not affected by pH change in the range from 5.5 to 3.3, and maintained above 97.4%. Fly ash can improve SO2 absorption efficiency and DTHE. NO2 can accelerate the oxidation of bisulfite to sulfate and promote SO2 absorption. CO2 hardly influences on SO2 absorption efficiency, but the SO2 absorption capacity decreases with the increasing of CO2 partial pressure. Furthermore, the thermal stability and regenerability of FA were also evaluated by TG-DTG and XRD, respectively. The results demonstrate that FA with stable performances is a promising regenerative absorbent for the removal of SO2.

Fe3−xCuxO4 as highly active heterogeneous Fenton-like catalysts toward elemental mercury removal

A series of novel spinel Fe3−xCuxO4 (0<x<0.71) composites, synthesized by chemical co-precipitation method, are proposed synthesized to use as highly active heterogeneous Fenton-like catalysts to remove elemental mercury (Hg0) from the simulated flue gases. Inductively coupled plasma-Atomic emission spectrometry (ICP-AES), X-ray diffraction patterns (XRD), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) surface area, and X-ray photoelectron spectrometer (XPS) were used to characterize the catalysts. The catalysts were confirmed the presence of the redox pairs Fesurf2+/Fesurf3+ and Cusurf+/Cusurf2+ on the surface of the cubic structure. The performance of heterogeneous Fenton-like reactions for Hg0 removal was evaluated in a lab-scale bubbling reactor at the solution temperature of 50°C. The systematic studies on the effects of different catalysts, H2O2 concentration and solution pH values on Hg0 removal efficiencies were performed. The recycling of the Fe3−xCuxO4 catalysts in Fenton-like solution is stable and Hg0 removal efficiency remain above 90% after 3 cycles. The active hydroxyl radical (OH) generated during heterogeneous Fenton-like reactions was confirmed through electron spin resonance (ESR) spin-trapping technique. The Hg0 removal mechanism has been discussed based on the experimental and analytical results.

Removal of sulfur dioxide from flue gas using the sludge sodium humate.

This study shows the ability of sodium humate from alkaline treatment sludge on removing sulfur dioxide (SO2) in the simulated flue gas. Experiments were conducted to examine the effect of various operating parameters, like the inlet SO2 concentration or temperature or O2, on the SO2 absorption efficiency and desulfurization time in a lab-scale bubbling reactor. The sludge sodium humate in the supernatant after alkaline sludge treatment shows great performance in SO2 absorption, and such efficiency can be maintained above 98% with 100 mL of this absorption solution at 298 K (flue gas rate of 0.12 m3/h). The highest SO2 absorption by 1.63 g SHA-Na is 0.946 mmol in the process, which is translated to 0.037 g SO2 g−1 SHA-Na. The experimental results indicate that the inlet SO2 concentration slightly influences the SO2 absorption efficiency and significantly influences the desulfurization time. The pH of the absorption solution should be above 3.5 in this process in order to make an effective desulfurization. The products of this process were characterized by Fourier transform infrared spectroscopy and X-ray diffraction. It can be seen that the desulfurization products mainly contain sludge humic acid sediment, which can be used as fertilizer components.

Removal of NO by using Fenton reagent solution in a lab-scale bubbling reactor

Removal of NO was studied in a lab-scale bubbling reactor. Effects of operation parameters such as pH value, H2O2 concentration, NO inlet concentration and reaction temperature on NO removal efficiency were investigated. The operation parameters included 250–1000ppm NO, 0.5–1.5mol/L H2O2, FeSO4 0.05mol/L, 2–6 pH, 25–70°C. As can be seen from the experimental results, pH value had a great impact on NO removal efficiency. The experimental results indicated that the gas–liquid reaction between NO and Fenton reagent solution was liquid-film controlled as NO inlet concentration exceeded 600ppm. And NO removal efficiency decreased with increasing reaction temperature.

Removal of SO2 from Flue Gas by Sodium Humate Solution

A novel process of flue gas desulfurization (FGD) by sodium humate (HA−Na) solution was developed. Experiments were carried out to examine the effect of various operating parameters, such as the HA−Na concentration, pH, temperature, gas flow rate, O2 concentration, SO2 inlet concentration, and NO2, on the SO2 absorption efficiency and desulfurization time in a lab-scale bubbling reactor. The experimental results indicate that the HA−Na concentration significantly influences the desulfurization time but has little effect on the SO2 absorption efficiency. The desulfurization time increases with the HA−Na concentration reaching 0.06 g/mL, and after this value, it begins to decrease. The SO2 absorption efficiency maintains 99% when pH is above 4.5. A low gas flow rate and low temperature are favorable to SO2 absorption. The increase of the SO2 inlet concentration improves the mass transfer of SO2 and accelerates the SO2 consumption rate. NO2 coexisting with SO2 can promote SO2 absorption because it may speed ...

Mass transfer in the absorption of SO2 and NOx using aqueous euchlorine scrubbing solution

Attempts have been made to generate euchlorine gas by chlorate-chloride process and to utilize it further to clean up SO2 and NO(x) from the flue gas in a lab scale bubbling reactor. Preliminary experiments were carried out to determine the gas and liquid phase mass transfer coefficients and their correlation equations have been established. Simultaneous removal of SO2 and NO(x) from the simulated flue gas using aqueous euchlorine scrubbing solution has been investigated. Euchlorine oxidized NO into NO2 completely and the later subsequently absorbed into the scrubbing solution in the form of nitrate. SO2 removal efficiency around 100% and NO(x) removal efficiency around 72% were achieved under optimal conditions. Mass balance has been confirmed by analyzing the sulfate, nitrate, euchlorine and chloride ion using ion chromatograph/auto-titrator and comparing it with their corresponding calculated values.

Study on the removal of NO x from simulated flue gas using acidic NaClO 2 solution

The study on the removal of NO x from simulated flue gas has been carried out in a lab-scale bubbling reactor using acidic solutions of sodium chlorite. Experiments were performed at various pH values and inlet NO concentrations in the absence or presence of SO 2 gas at 45°C. The effect of SO 2 on NO oxidation and NO 2 absorption was critically examined. The oxidative ability of sodium chlorite was investigated at different pH values and it was found to be a better oxidant at a pH less than 4. In acidic medium, sodium chlorite decomposed into ClO 2 gas, which is believed to participate in NO oxidation as well as in NO 2 absorption. A plausible NO x removal mechanism using acidic sodium chlorite solution has been postulated. A maximum NO x removal efficiency of about 81% has been achieved.

Removal of NO from flue gas by aqueous chlorine-dioxide scrubbing solution in a lab-scale bubbling reactor

The present study attempts to clean up nitric oxide from the simulated flue gas using aqueous chlorine-dioxide solution in the bubbling reactor. Chlorine-dioxide is generated by chloride–chlorate process. Experiments are carried out to examine the effect of various operating variables like input NO concentration, presence of SO 2, pH of the solution and NaCl feeding rate on the NO x removal efficiency at 45 °C. Complete oxidation of nitric oxide into nitrogen dioxide occurred on passing sufficient ClO 2 gas into the scrubbing solution. NO is finally converted into nitrate and ClO 2 is reduced into chloride ions. A plausible reaction mechanism concerning NO x removal by ClO 2 is suggested. DeNO x efficiency increased slightly with the increasing input NO concentration. The presence of SO 2 improved the NO 2 absorption but pH of solution showed marginal effect on NO 2 absorption. NO x removal mechanism changed when medium of solution changed from acidic to alkaline. A constant NO x removal efficiency of about 60% has been achieved in the wide pH range of 3–11 under optimized conditions.

Simultaneous removal of SO 2 and NO by wet scrubbing using aqueous chlorine dioxide solution

The present study attempts to generate chlorine dioxide (ClO 2) gas continuously by chlorate–chloride process and to utilize it further to clean up SO 2 and NO x gases simultaneously from the flue gas in the lab-scale bubbling reactor. Experiments were carried out to examine the effect of various operating parameters like input SO 2 concentration, input NO concentration, pH of the reaction medium, and ClO 2 feeding rate on the SO 2 and NO x removal efficiencies at 45 °C. Complete oxidation of NO into NO 2 occurred on passing sufficient ClO 2 gas into the scrubbing solution. SO 2 removal efficiency of about 100% and NO x removal efficiency of 66–72% were achieved under optimized conditions. NO x removal efficiency decreased slightly with increasing pH and NO concentration. Input SO 2 concentration had marginal catalytic effect on NO 2 absorption. No improvement in the NO x removal efficiency was observed on passing excess of chlorine dioxide in the scrubbing solution.