Dar-Ren Ji

Combined photolysis and catalytic ozonation of dimethyl phthalate in a high-gravity rotating packed bed

In this study, a high-gravity rotating packed bed (HGRPB) was used as a catalytic ozonation reactor to decompose dimethyl phthalate (DMP), an endocrine disrupting chemical commonly encountered. The HGRPB is an effective gas-liquid mixing equipment which can enhance the ozone mass transfer coefficient. Platinum-containing catalyst (Pt/-Al2O3) of Dash 220N and ultra violet (UV) lamp were combined in the high-gravity ozonation (HG-OZ) system to enhance the self-decomposition of molecular ozone in liquid to form highly reactive radical species. Different combinations of HG-OZ with Dash 220N and UV for the degradation of DMP were tested. These include HG-OZ, HG catalytic OZ (HG-Pt-OZ), HG photolysis OZ (HG-UV-OZ) and HG-UV-Pt-OZ. The result indicated that all the above four ozonation processes result in significant decomposition of DMP and mineralization of total organic carbon (TOC) at the applied ozone dosage per volume of liquid sample of 1.2gL(-1). The UV and Pt/gamma-Al2O3 combined in HG-OZ can enhance the TOC mineralization efficiency (eta(TOC)) to 56% (via HG-UV-OZ) and 57% (via HG-Pt-OZ), respectively, while only 45% with ozone only. The process of HG-UV-Pt-OZ offers the highest eta(TOC) of about 68%.

Kinetics and equilibrium of desorption removal of copper from magnetic polymer adsorbent.

This study examined the desorption of copper ions, which were adsorbed on the magnetic polymer adsorbent (MPA) of polyvinyl acetate-iminodiacetic acid (M-PVAC-IDA), by ethylenediaminetetraacetic acid (EDTA). Stage-wise desorptions were applied to remove the Cu(II) ions from the Cu(II) adsorbed M-PVAC-IDA (A-M-PVAC-IDA). About seven desorption runs were needed to regenerate the A-M-PVAC-IDA. The Cu(II) desorbed M-PVAC-IDA (D-M-PVAC-IDA) was then reused to adsorb the Cu(II) ions from the Cu(II) ions-containing solution. The cyclic adsorption and desorption operations (CADOs) were performed to further elucidate the kinetics and equilibria of the desorption system of EDTA/A-M-PVAC-IDA and the adsorption system of Cu(II)-containing solution/D-M-PVAC-IDA. Two simple kinetic models, the pseudo-first-order equation and pseudo-second-order equation, were employed to simulate the kinetic behaviors of adsorption and desorption. With respect to the kinetics of adsorption behavior, the simulated results by both kinetic models exhibit good agreement with the experimental data. However, the adsorption capacities (q(e)) estimated by the pseudo-first-order equation are more accurate in comparison with those simulated by the pseudo-second-order equation. As for the desorption kinetics, the examination of correlation coefficients of model fittings of data shows that the pseudo-first-order kinetic model gives the better agreement for the cases with different initial solid-phase concentrations and can accurately compute the equilibrium concentrations of solid-phase. The values of q(e) after CADOs are consistent with the predicted results via the previous work, evidencing that the adsorption behavior and the characteristics of the regenerated adsorbent of D-M-PVAC-IDA were not altered. In the experiments of desorbing copper ions and CADOs, the desorption isotherm was set up. The Freundlich and Langmuir adsorption (or desorption) isotherms were used to simulate the equilibrium of desorption. The results indicate that the Freundlich equation shows better agreement with the experimental data than the Langmuir equation. The information thus obtained is useful for the better use of M-PVAC-IDA on the removal of heavy mental ions of Cu(II) from the Cu(II) ion-containing water solution with the consideration of its regeneration.

Decomposition of 2-naphthalenesulfonate in aqueous solution by ozonation with UV radiation

This study investigates the ozonation of 2-naphthalenesulfonate (2-NS) combined with ultraviolet (UV) radiation. Naphthalenesulfonic acids are of importance as dye intermediates for the dye and textile auxiliary industries. Its derivatives, such as 2-NS, have been found in rivers and tannery effluents causing pollution problems. Thus, the 2-NS is of concern for the aquatic pollution control especially in the surface and waste waters. Ozonation combined with UV radiation is employed for the removal of 2-NS in the aqueous solution. Semibatch ozonation experiments were proceeded under different reaction conditions to study the effects of ozone dosage and UV radiation on the oxidation of 2-NS. The concentrations of 2-NS and sulfate are analyzed at specified time intervals to elucidate the decomposition of 2-NS. In addition, values of pH and oxidation reduction potential are continuously measured in the course of experiments. Total organic carbon is chosen as a mineralization index of the ozonation of 2-NS. The mineralization of 2-NS via the ozonation is remarkably enhanced by the UV radiation. These results can provide useful information for the proper removal of 2-NS in the aqueous solution by the ozonation with UV radiation.

Pt-catalyzed ozonation of aqueous phenol solution using high-gravity rotating packed bed

In this study, a high-gravity rotating packed bed (HGRPB or HG) was used as a catalytic ozonation (Cat-OZ) reactor to decompose phenol. The operation of HGRPB system was carried out in a semi-batch apparatus which combines two major parts, namely the rotating packed bed (RPB) and photo-reactor (PR). The high rotating speed of RPB can give a high volumetric gas-liquid mass transfer coefficient with one or two orders of magnitude higher than those in the conventional packed beds. The platinum-containing catalyst (Dash 220N, Pt/gamma-Al(2)O(3)) and activated alumina (gamma-Al(2)O(3)) were packed in the RPB respectively to adsorb molecular ozone and the target pollutant of phenol on the surface to catalyze the oxidation of phenol. An ultra violet (UV) lamp (applicable wavelength lambda=200-280 nm) was installed in the PR to enhance the self-decomposition of molecular ozone in water to form high reactive radical species. Different combinations of advanced oxidation processes (AOPs) with the HGRPB for the degradation of phenol were tested. These included high-gravity OZ (HG-OZ), HG catalytic OZ (HG-Cat-OZ), HG photolysis OZ (HG-UV-OZ) and HG-Cat-OZ with UV (HG-Cat-UV-OZ). The decomposition efficiency of total organic compound (eta(TOC)) of HG-UV-OZ with power of UV (P(UV)) of 16W is 54% at applied dosage of ozone per volume sample m(A,in)=1200 mg L(-1) (reaction time t=20 min), while that of HG-OZ without the UV irradiation is 24%. After 80 min oxidation (m(A,in)=4800 mg L(-1)), the eta(TOC) of HG-UV-OZ is as high as 94% compared to 82% of HG-OZ process. The values of eta(TOC) for HG-Cat-OZ process with m(S)=42 g are 56% and 87% at m(A,in)=1200 and 4800 mg L(-1), respectively. By increasing the catalyst mass to 77 g, the eta(TOC) for the HG-Cat-OZ process reaches 71% and 90% at m(A,in)=1200 and 4800 mg L(-1), respectively. The introduction of Pt/gamma-Al(2)O(3) as well as UV irradiation in the HG-OZ process can enhance the eta(TOC) of phenol significantly, while gamma-Al(2)O(3) exhibits no significant effect on eta(TOC). For the HG-Cat-UV-OZ process with m(S)=42 g, the values of eta(TOC) are 60% and 94% at m(A,in)=1200 and 4800 mg L(-1), respectively. Note that the decomposition of TOC via HG-UV-OZ is already vigorous. Thus, the enhancing effect of catalyst on eta(TOC) is minor.

Adsorption Removal of Environmental Hormones of Dimethyl Phthalate Using Novel Magnetic Adsorbent.

Magnetic polyvinyl alcohol adsorbent M-PVAL was employed to remove and concentrate dimethyl phthalate DMP. The M-PVAL was prepared after sequential syntheses of magnetic Fe3O4 (M) and polyvinyl acetate (M-PVAC). The saturated magnetizations of M, M-PVAC, and M-PVAL are 57.2, 26.0, and 43.2 emu g−1 with superparamagnetism, respectively. The average size of M-PVAL by number is 0.75 μm in micro size. Adsorption experiments include three cases: (1) adjustment of initial pH (pH0) of solution to 5, (2) no adjustment of pH0 with value in 6.04–6.64, and (3) adjusted pH0 = 7. The corresponding saturated amounts of adsorption of unimolecular layer of Langmuir isotherm are 4.01, 5.21, and 4.22 mg g−1, respectively. Values of heterogeneity factor of Freundlich isotherm are 2.59, 2.19, and 2.59 which are greater than 1, revealing the favorable adsorption of DMP/M-PVAL system. Values of adsorption activation energy per mole of Dubinin-Radushkevich isotherm are, respectively, of low values of 7.04, 6.48, and 7.19 kJ mol−1, indicating the natural occurring of the adsorption process studied. The tiny size of adsorbent makes the adsorption take place easily while its superparamagnetism is beneficial for the separation and recovery of micro adsorbent from liquid by applying magnetic field after completion of adsorption.

Catalytic destruction of vinyl chloride over an alumina–supported platinum catalyst

In this study, vinyl chloride (VC), the primary material for manufacturing polyvinyl chloride (PVC), is decomposed via catalytic oxidation (C-OX) using Pt/γ-Al2O3 catalyst. The effects of related major factors such as reaction temperature (T) and gas hourly space velocity on the conversion of VC (X) were examined. The values of T for achieving conversions of 50% and 90% are 504 and 580 K with C-OX, respectively, whereas those without Pt/γ-Al2O3 (i.e., thermal oxidation, T-OX) are 900 and 983 K, respectively, thus indicating that C-OX significantly reduces T for effective oxidation of VC to form CO2, HCl, and Cl2 when compared with T-OX. The mineralizations of carbon in VC to form CO2 are 75.5% and 38% for C-OX and T-OX, respectively, at 90% X. The conversions of chlorine atom in 1,2-dichloroenane (DCEA) to Cl in HCl and Cl2 are approximately 42% and 50.8% for C-OX and T-OX, respectively, at 90% X. These results indicate that the Pt/γ-Al2O3 catalyst exhibits remarkable performance for the mineralizations to form CO2 even though a proportion of chlorine atoms are adsorbed on the Pt surface. The Eley–Rideal model can be used to describe the experimental results, thus yielding activation energy and frequency factor values of 49.0 kJ mol−1 and 1.77 × 106 s−1, respectively. The obtained information and kinetic parameters are useful for the rational design and operation of C-OX process for the abatement of VC.

Decomposition and Mineralization of Dimethyl Phthalate in an Aqueous Solution by Wet Oxidation

Dimethyl phthalate (DMP) was treated via wet oxygen oxidation process (WOP). The decomposition efficiency η DMP of DMP and mineralization efficiency η TOC of total organic carbons were measured to evaluate the effects of operation parameters on the performance of WOP. The results revealed that reaction temperature T is the most affecting factor, with a higher T offering higher η DMP and η TOC as expected. The η DMP increases as rotating speed increases from 300 to 500 rpm with stirring enhancement of gas liquid mass transfer. However, it exhibits reduction effect at 700 rpm due to purging of dissolved oxygen by overstirring. Regarding the effects of pressure P T, a higher P T provides more oxygen for the forward reaction with DMP, while overhigh P T increases the absorption of gaseous products such as CO2 and decomposes short-chain hydrocarbon fragments back into the solution thus hindering the forward reaction. For the tested P T of 2.41 to 3.45 MPa, the results indicated that 2.41 MPa is appropriate. A longer reaction time of course gives better performance. At 500 rpm, 483 K, 2.41 MPa, and 180 min, the η DMP and η TOC are 93 and 36%, respectively.