Kitirote Wantala

Optimizing chemical oxygen demand removal from synthesized wastewater containing lignin by catalytic wet-air oxidation over CuO/Al2O3 catalysts

In this study, 10% CuO/Al2O3 catalyst was used in a catalytic wet-air oxidation process to remove chemical oxygen demand (COD) and color from experimentally designed wastewater containing lignin. The catalyst was prepared using an impregnation method and was characterized by X-ray diffraction (XRD), atomic absorption spectroscopy (AAS), and Brunauer-Emmett-Teller method (BET) for surface area before use. A series of Box-Behnken design (BBD) experiments were used to identify the conditions (temperature, pressure, reaction time, and catalysts) necessary for the COD removal process. The predicted model had R2 and R2adj correlation coefficients of 0.98 and 0.97, respectively. Pressure only and the interaction effect between temperature and pressure were found to have a significant effect on COD removal (both confidence interval [CI] 95%). Finally, response surface methodology (RSM)-optimized results suggested that 92% of COD could be removed in 1 L of experimental wastewater with a lignin concentration 350 g/L in 120 min under the following conditions: a reaction temperature of 185 °C, a pressure of 10 bars, and catalyst loading of 1 mg/L. The experiment, performed in triplicate, yielded a COD removal of 90 ± 2%. The results are believed to be of importance to pulp and paper industrial wastewater treatment and other similar applications. Implications: Catalytic wet-air oxidation (CWAO) has been used as an alternative to overcome problems related to the high temperatures and pressures required by the traditional wet-air oxidation. CWAO has been widely applied to treat various industrial wastewaters. To reduce the overall operational cost, it is necessary to identify the optimal condition required when designing wastewater treatment plant processes. In this work, the authors had successfully demonstrated the application of response surface methodology (RSM) with the Box-Behnken design (BBD) as a means of elucidating the complicated interaction effects between parameters.

Photocatalytic Degradation of Alachlor on Fe-TiO2-Immobilized on GAC under Black Light Irradiation Using Box-Behnken Design

The aim of this work was focused on the photocatalytic degradation of alachlor from aqueous solution using 10%wt Fe-TiO2, as 0.1%wt of Fe doped into TiO2 structure, immobilized on granular activated carbon (GAC) under black light irradiation. The extended photocatalytic conditions were studied as functions of catalyst loading, number of black light, and initial pH of solution using Response Surface Method (RSM) based on Box-Behnken design (BBD). Characterizations of the photocatalyst by TGA-DTA, and XRD were investigated. Photocatalyst was calcined at 400°C under nitrogen atmosphere. As a Result of calcinations, photocatalyst consisted of only graphite crystallite while the crystallite phases of TiO2 were not observed. The degradation results showed that the photocatalytic process gave the highest percent degradation comparing with adsorption and photolysis processes. The effects of three operating variables which are catalyst loading, number of black light, and initial pH of solution on the degradation efficiency of alachlor were examined. Photocatalyst loading was only significant parameter effecting for photocatalytic degradation of alachlor. The photocatalytic degradation slightly increased with increasing of number of black light while pH of solution did not affect photocatalytic degradation of alachlor. The photocatalytic process and adsorption process were affected from the initial alachlor concentrations as well.

Photocatalytic paraquat degradation over TiO2 modified by hydrothermal technique in alkaline solution

Abstract In the present research, titanium nanotubes were synthesized via the soft hydrothermal method. A study on the effect of the synthesizing parameters such as aging temperature and time of the hydrothermal process on the photocatalytic paraquat degradation was explored. Central Composite Design (CCD) was used to determine the influence of the preparation parameter on the optimal condition, main and interaction effects on crystalline size, percent paraquat removal by adsorption and photocatalytic degradation as responses. The XRD pattern of the synthesized nanomaterial reported the anatase phase of titania nanotubes. SEM image of the prepared nanomaterial clearly indicated the agglomerated with tubular structure. Band gap energy of the nanotubes was found lower than that of the pure anatase TiO2. Paraquat removal by adsorption is more effective than by photocatalytic degradation. The error of the model remains insignificant for all the three responses.

Optimal Decolorization Efficiency of Reactive Red 3 by Fe-RH-MCM-41 Catalytic Wet Oxidation Coupled with Box-Behnken Design

The reactive red 3 was degraded by catalytic wet oxidation process over Fe-RH-MCM-41 prepared by Direct Hydrothermal Technique (DHT) at Si/Fe molar ratio of 10 using silica from rice husk. The extended reaction conditions were studied as a function of reaction temperatures, initial H2O2 concentrations and initial pH of solutions designed by Box-Behnken design (BBD) based on Response Surface Methodology (RSM) to achieve the optimal condition and interaction of independent variables. The characterizations of catalyst were studied by XRD, BET surface area and TEM to explain the morphology of surface and to confirm the hexagonal structure. The results showed the 2theta peak can be indexed to hexagonal lattice that also confirmed by TEM result and surface area about 650 m2/g. All of independent variables showed significant on the degradation of reactive red 3 except for initial H2O2 concentration.

Metal Adsorbent Prepared from Coir Pith as Agricultural Waste: Adsorption of Zn(II) and Pb(II) from Aqueous Solution

Adsorption of Zn(II) and Pb(II) from aqueous solution were studied by using modified coir pith as an adsorbent. The extended adsorption conditions were investigated as a function of calcination temperature, contact time, adsorbent size, initial pH of solution and initial Zn(II) and Pb(II) concentrations. The adsorption capacity increased rapidly in first 5 minute and reached equilibrium in 120 minutes for Zn(II) and 10 minutes for Pb(II). In case of Zn(II); the results showed that the calcination temperature of modified coir pith above 600oC gave the higher adsorption capacity. The sizes of modified coir pith have no effect on the adsorption capacity. The adsorption capacity increased with increasing initial solution pH value. In case of Pb(II); the calcination temperature of modified coir pith showed no effect on the adsorption capacity. The sizes of modified coir pith showed a little effect on the adsorption capacity. The adsorption capacity increased with increasing of initial solution pH value up to pH of 3 and then stable. The results also corresponded with the Langmuir and Freundlich isotherms and pseudo second order kinetic adsorption models. The modified coir pith gave a higher Zn(II) and Pb(II) adsorption capacity of 29.33 mg Zn(II)/g adsorbent and 36.50 mg Pb(II)/g adsorbent, respectively.

Manganese Loaded on Titania Surface by Impregnation Method for Photocatalytic Degradation of Reactive Red-3 Dye

The aim of this work focused on the preparation of Mn2+ doped on TiO2 by impregnation method for the photocatalytic degradation of Reactive Red-3 dye aqueous solution. Characterizations of the photocatalyst were carried out by using XRD, BET, SEM and UV-DRs. The extended photocatalysis were studied as functions of %wt Mn2+ (0%, 0.05%, 0.1%), pollutant concentration, solution pH and catalyst loading using Response Surface Method (RSM) based on Box-Behnken design. Based on results found that the anatase phase was not affected by Mn2+ added on the surface of TiO2 whereas the rutile phase increased with increasing Mn2+ contents. The band gap energy of Mn2+ doped on TiO2 did not show in red shift but it exhibited higher absorbance than neat TiO2 in visible region. The surface area was insignificantly changed for Mn2+ doped on TiO2. The degradation results were investigated that pollutant concentration, pH of solution and loading of Mn2+ on TiO2 were significant parameters effecting on photocatalytic degradation of Reactive Red-3 dye. The existence of Mn2+ on TiO2 decreased the activity of rectaion. The optimum condition was 0%wt of Mn2+, 10 ppm of Reactive Red-3, pH 4 and 4.0 g/L of catalyst loading.

Toluene Degradation by Thermal Catalytic Oxidation over K-OMS-2 Catalysts

The goal of this research was to synthesize two different catalysts, namely K-OMS-2 and MnOx. The K-OMS-2 was an octahedral manganese complex prepared by hydrothermal method, while manganese oxide (MnOx) was directly synthesized by precipitation method. Both catalysts were employed to decompose toluene, an organic solvent that is widely used in industries. The catalysts were characterized by means of X-ray diffraction (XRD) and N2-physorption. The surface areas of K-OMS-2 and MnOx were 83.50 and 20.04 m2/g, respectively. The precipitation route gave XRD patterns of γ-Mn2O3 structure, and a successful structure of an octahedral molecular sieve manganese oxide was obtained by the hydrothermal method. The toluene degradation was carried out in gas hourly space velocity (GHSV) range of 20,000-60,000 h-1 with toluene concentration of 7,700 ppmv. The higher GHSV over K-OMS-2 gave the lower contact time consequently resulting in the lower %toluene degradation, whereas the best GHSV over γ-Mn2O3 was suitable at 40,000 h-1. The complete oxidation temperature of toluene over K-OMS-2 occurred at 260 °C and was lower than the temperature by γ-Mn2O3 at 300 °C. The higher surface area of K-OMS-2 may not facilitate internal toluene diffusion to active K-OMS-2 sites because molecular toluene (5.6 Å) cannot migrate through its smaller pore diameter (4.6 Å); however, the fully oxidized K-OMS-2 can provide higher average oxidation state (AOS) and higher amount of lattice oxygen assisting toluene degradation compared to γ-Mn2O3. The full factorial design of experiment (DOE) exhibited a strong effect of temperature and catalyst types on toluene removal; in contrast gas hour space velocity (GHSV) exhibited no significant effect on %toluene removal even with increasing GHSV.

Parameter Screening for the Important Factors Influencing the As(V) Adsorption Using a Plackett-Burman Design

The adsorption efficiency of As (V) ions from an aqueous solution was investigated. The adsorption experiments were carried out in a batch reactor. The effects of operating parameters; i.e. the absorbent dose (g/L), the pH, the adsorption temperature (°C), the As (V) initial concentration (ppb), and type of adsorbents, on the adsorption efficiencies were studied. A PlackettBurman experimental design was used to screen for the important factors that influence As (V) adsorption. It has been found that the most important effect on the As (V) adsorption capacity was the type of adsorbent. The factor importance could be written in descending order as follows: the type of adsorbents, the adsorbent dose, the As (V) initial concentration, the adsorption temperature, and the pH.