Removal of Color and Chemical Oxygen Demand from Landfill Leachate by Photocatalytic Process with AC/TiO2

AbstractThis research paper has presented a simplified sol-gel preparation method for a hybrid activated carbon/titanium dioxide (AC/TiO2) photocatalyst. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Brunauer-Emmett-Teller (BET) analysis were utilized to examine the surface properties of the AC/TiO2 photocatalyst. The analysis results showed that the TiO2 particles coated on the AC surface were of anatase phase and that the surface area, pore volume and pore size of the hybrid AC/TiO2 photocatalyst were reduced in relation to those of the uncoated AC. The photocatalytic performances of the hybrid photocatalyst were evaluated for color and COD removals through experimentation with landfill leachate under UVA irradiation of two different intensities. The experiments revealed that the coating of TiO2 onto AC enhanced the removal efficiencies and that the increased UVA intensity boosted the photoactivity. The high photoactivity under UVA irradiation makes the proposed hybrid AC/TiO2 photocatalyst an ideal photocatalyst

Application of Life Cycle Assessment Method for Environmental Impact Assessment of Fired Brick Production Plant in Thailand

In many Asian countries, fired bricks are produced by burning raw bricks in a rudimentary clamp kiln without pollution control mechanisms, a practice which contributes to several kinds of environmental impact. This research investigated the inputs and outputs associated with production of fired bricks using the rice husk-fuelled clamp kiln. Data collected included raw material use, energy, products, emissions and kiln temperatures. To quantify environmental impacts, the consequential-focused life cycle assessment (LCA) approach was adopted. The impacts were assessed in terms of fuel substitution as the acquisition of another fuel was required to substitute for electricity. The findings indicated that the clamp kiln technology produced low CO2 emissions per unit of production and per unit of energy input, despite poor specific energy consumption. The LCA analysis indicated that the use of rice husk was the major contributor to environmental impact, and that abiotic depletion of fossil fuels represented the environmental hotspot. To improve combustion efficiency, the clamp kilns should be either insulated or replaced with more efficient kiln technology, in conjunction with the use of rice husk

Photocatalytic reduction of nitrate over TiO2 and Ag-modified TiO2

AbstractThis research work presents the efficiency of the TiO2 and Ag–TiO2 thin films prepared by the sol–gel method and coated onto the surface of 304 stainless steel sheets used in the photocatalytic nitrate reduction processes. The Ag–TiO2 thin films had the weight by weight (w/w) ratio of Ag+/TiO2 of 0.1% as Ag atom. The XRD results showed that the crystalline phase structure of TiO2 on the Ag–TiO2 thin films was anatase. The optical band gaps of the TiO2 and 0.1% Ag–TiO2 thin films were respectively 3.27 and 2.70 eV, while the surface of the prepared catalysts was hydrophobic with the respective average water contact angles of 94.8° and 118.5° for the TiO2 and 0.1% Ag–TiO2 thin films. The net efficiencies of photocatalytic nitrate reduction of TiO2 and 0.1% Ag–TiO2 were 41.4% and 70.0%, respectively. The loading of Ag only influenced the nitrate removal efficiency without affecting the stoichiometric ratio of formate to nitrate. The net stoichiometric ratio of formate to nitrate of all experiments was 2.8:1.0, which is close to the stoichiometric ratio of 2.5:1.0 of the nitrate reduction to nitrite and then to nitrogen gas

Feasible Application of PCLake Model to Predict Water Quality in Tropical Reservoirs

The PCLake model has not previously been used for tropical reservoirs. This study attempted to apply the PCLake model to predict the chlorophyll a concentrations (Chl-a) in a tropical reservoir in Thailand. Sensitivity analyses were performed for the constants affecting the prediction of Chl-a in the phytoplankton module. The model calibration was performed by using the adjusted value of the most sensitive constant with the observed data from July to December 2020. The effects of the initial trophic state of the reservoir on the simulated Chl-a were evaluated. The results showed that Chl-a were sensitive to six constants. Among these constants, the value of the specific extinction of detritus (cExtSpDet) was adjusted using the calculated values from the typical limnological parameters of the studied reservoir. Statistical analyses of the results of calibration and the subsequent validation with the observed data from February to September 2022 were listed as follows: NSE=0.55 and 0.37, RSR=0.67 and 0.79, and PBIAS=27% and 9%, respectively. The initial trophic state of the reservoir had no influence on the long-term prediction of Chl-a. This preliminary effort indicates that the PCLake model can be used to predict Chl-a, which is representative of algal biomass in tropical reservoirs and is essential to water quality models, without complex modifications

Photocatalytic Activity of Toluene under UV-LED Light with TiO2 Thin Films

Titanium dioxide (TiO2) and ferric-doped TiO2 (Fe-TiO2) thin films were synthesized on the surface of 304 stainless steel sheets using a simplified sol-gel preparation method. The Fe-TiO2 thin films were prepared with weight-to-volume ratios of /TiO2 of 0.3%, 0.5%, and 0.7%, respectively. The crystalline phase structures of the prepared TiO2 and Fe-TiO2 thin films were entirely anatase. The measured optical band gaps of the TiO2, 0.3% Fe-TiO2, 0.5% Fe-TiO2, and 0.7% Fe-TiO2 thin films were 3.27, 3.28, 3.22, and 2.82 eV, respectively. The grain sizes and other physical properties of the prepared thin films were also reported. The kinetics of the photocatalytic processes under a UV-LED light source could be explained by the Langmuir-Hinshelwood kinetic model with the specific rates of , , , and  , for TiO2, 0.3% Fe-TiO2, 0.5% Fe-TiO2, and 0.7% Fe-TiO2, respectively. An increase in dopant concentration could enhance the photocatalytic activity of toluene decomposition as a result of lower optical band gaps, smaller grain size, and higher surface area

Effects of Initial Nitrate Concentrations and Photocatalyst Dosages on Ammonium Ion in Synthetic Wastewater Treated by Photocatalytic Reduction

Ammonium (NH4+) is an undesirable by-product of photocatalytic nitrate (NO3−) reduction since it is harmful to aquatic life once it converts into ammonia (NH3). This research investigated the removal efficiency of NO3− and for the first time quantified the relationships of initial nitrate concentrations ([NO3−]0) and photocatalyst dosages on the remaining ammonium (NH4+) in synthetic wastewater using photocatalytic reduction process with either nanoparticle titanium dioxide (TiO2) or 1.0%Ag-TiO2 under Ultraviolet A (UVA). The experiments were systematically carried out under various combinations of [NO3−]0 (10, 25, 50, 80, and 100 mg-N/L) and photocatalyst dosages (0.1, 0.5, 1.0, and 2.0 g). The NO3− removal efficiency of both photocatalysts was 98.96-99.98%, and the catalytic selectivity products were nitrogen gas (N2), nitrite (NO2−), and NH4+. Of the two photocatalysts under comparable experimental conditions, 1.0%Ag-TiO2 provided better NO3− removal efficiency. For both photocatalysts, the remaining NH4+ was predominantly determined by [NO3−]0; higher [NO3−]0 led to higher NH4+. Multiple linear regression analysis confirmed the dominant role of [NO3−]0 in the remaining NH4+. The photocatalyst dosage could play an essential role in limiting NH4+ in the treated wastewater, with large variation in [NO3−]0 from different sources