Effect of Calcination Temperature on Performance of Photocatalytic Reactor System for Seawater Pretreatment

Conservative desalination technology including distillation requires high energy and cost to operate. Hence, pretreatment process can be done prior to desalination to overcome energy demand and cost reduction. Objective of this research is to study the effect of calcination temperature of hybrid catalyst in photocatalytic reactor system in the seawater desalination, i.e. salt removal in the seawater. The catalyst was synthesized via wet impregnation method with 1:1 weight ratio of TiO2 and activated oil palm fiber ash (Ti:Ash). The catalyst was calcined at different temperature, i.e. 500 oC and 800 oC. The study was carried out in a one liter Borosilicate photoreactor equipped with mercury light of 365 nanometers for two hours with 400 rpm mixing and catalyst to seawater sample weight ratio of 1:400. The Chemical Oxygen Demand (COD), pH, dissolved oxygen (DO), turbidity and conductivity of the seawater were analyzed prior and after the testing. The fresh and spent catalysts were characterized via X-Ray Diffractogram (XRD and Nitrogen physisorption analysis. The calcination temperature significantly influenced the adsorption behaviour and photocatalytic activity. However, Ti:Ash which calcined at 800 oC has less photocatalytic activity. It might be because the surface of fiber ash was sintered after calcined at high temperature. The Ti:Ash catalyst that calcined at 500 oC was found to be the most effective catalyst in the desalination of seawater by reducing the salt concentration of more than 9 % compared to Ti:Ash calcined at 800 oC. It can be concluded that catalyst calcination at 500 °C has better character, performance and economically feasible catalyst for seawater desalination.

Oil palm fiber ash characterization and application in solar evaporator for seawater desalination

Solar evaporator is a non-conventional technology, cheapest, cleanest process and simplest technique for seawater desalination. However, low thermal efficiency is the main problem in solar evaporation process. The objective of this paper is to study the effect of oil palm fiber ash application in seawater evaporation of seawater to produce clean water. The spent and fresh oil palm fiber ash were characterized by using Nitrogen Adsorption (BET), X Ray Detector (XRD) and Scanning Electromagnetic Microscope (SEM). The investigation was conducted in a 0.4m x 0.45m x 0.15m basin type solar evaporator. The oil palm ash to seawater mass ratio was varied from 1:50 to 1:500. The investigation was carried out for eight hours in sunny daylight. The water qualities including pH, conductivity, total dissolve solid (TDS), chemical oxygen demand (COD) and turbidity of the seawater and the evaporated water were determined. It was found that the addition of oil palm fiber ash in the seawater increased the seawater temperature to 57 °C when the oil palm ash to seawater mass ratio of 1:100 was used. The maximum temperature was achieved at 1:00 pm. About 12 % of evaporated was produced at the same condition. Interestingly, the COD value of seawater reduced drastically when oil palm fiber ash was used. The pH of the seawater increased slightly after the investigation might be due to the mineral content of oil palm fiber ash content which rich in CaO. It can be concluded that the application of oil palm fiber ash improve the performance of the solar evaporator and increase the production of evaporated water

Hybrid photocatalyst for seawater purification : catalyst composition

Hybrid photocatalyst of Titanium Dioxide (TiO2) catalyst become an attractive alternative promoter for seawater purification. The effect of catalyst composition in the seawater purification via photocatalytic reaction was investigated. Synthesis of a highly active solid catalyst is investigated by loading the different weight ratio of TiO2 on activated palm oil fiber ash through wet impregnation technique. The prepared catalysts were characterized by X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Brunauer Emmett Teller (BET). The catalyst was tested with seawater (weight ratio of catalyst to seawater of 1:400). The experiment was conducted in a 1 L Borosilicate photoreactor and mercury light with 365 nm wavelength was used. The performance of the catalyst was tested for two hours. The Chemical Oxygen Demand (COD), pH, Conductivity, Turbidity, Biochemical Oxygen Demand (BOD), Total Dissolved Solid (TDS) and Dissolved Oxygen (DO) of the seawater was analysed prior and after the testing. Better quality of water was obtained. SEM images show that the fiber ash became a good supporter for TiO2. TiO2 was well dispersed on fiber ash surface after the impregnation. BET indicates that the catalyst pore structure was mesoporous. The XRD result also indicates that the TiO2 has anatase crystal while fiber ash has quartz crystal. The solid solution might form too. The weight ratio of fibre ash to TiO2 of Ti:Ash 50:50 were found to be the most effective catalyst in purification of seawater by reducing 10.86% of salt concentration. In conclusion, the photocatalysis process is able to provide an alternative effective treatment for seawater purificatio

Titanium dioxide based hybrid photocatalyst for seawater desalination pre-treatment

The application of hybrid titanium dioxide (TiO2) photocatalyst in treating water resources has huge economic potential and an attractive alternative technology for seawater pre-desalination. The objective of this investigation is to study the effectiveness of photocatalytic reactor system via hybrid photocatalyst that content oil palm fiber ash (OPFA), TiO2 and metal promoter in the seawater desalination pre-treatment. The study was carried out in a one liter borosilicate photoreactor for 1 hr to 4 hrs. The catalyst to seawater sample weight ratio was varied from 1:300 to 1:500. The experiment was carried out by using mercury light (UV light) and halogen light (visible light). The chemical oxygen demand (COD), pH, dissolved oxygen (DO), turbidity, total dissolved solid (TDS) and conductivity of the seawater were analyzed prior and after the treatment. The fresh and spent catalysts were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), N2 adsorption, ultraviolet visible near-UV/near-infrared (UV/Vis/Nir), elemental analysis (carbon, hydrogen, nitrogen and sulphur (CHNS)) and X-ray fluorescence (XRF). The gas product was analyzed by using gas chromatography with thermal conductivity detector (GC-TCD). The TiO2 catalyst can reduce salt concentration for more than 7 % and decrease up to 8 % of COD. The OPFA was able to adsorb about 3 % of salt in either with the present or absent of lights. Furthermore, OPFA reduced seawater COD for more than 10 % the light presence and 4 % in without light present. The hybrid catalyst containing TiO2:Ash 50:50 was calcined at 500 °C, reduced more than 9 % of salt and 24 % of COD reduction in the seawater. It is found that the TiO2:Ash 50:50 catalyst has dual functions, ie. the catalyst was able to adsorb the salt and decompose the water contaminants resulting in lower conductivity and COD in the seawater. However, the hybrid TiO2:Ash 50:50 catalyst which calcined at 800 °C was only able to reduce 2 % of salt and 14 % of COD reduction in the seawater. Better TiO2:Ash 50:50 catalyst reactivity was achieved when UV light was used than visible light. Higher water temperature was observed when visible light was applied that leads to distillation dominating the process. The optimum parameters for photocatalytic reaction was obtained by using hybrid TiO2:Ash 50:50 catalyst when catalyst to water weight ratio was at 1:400 and operating for 2 hrs. Iron (Fe) and nickel (Ni) can be loaded into the catalyst. Fe loading in the catalyst was found to perform better than Ni. The best condition was obtained when visible light and TiO2:Ash:Fe 47.5:47.5:5 were used. The TiO2:Ash:Fe 47.5:47.5:5 reduced 16 % and 22 % of salt concentration and COD respectively. While, the TiO2:Ash:Ni 47.5:47.5:5 was only able to reduce up to 13 % of salt in the seawater and decrease 22 % of seawater COD at the same condition. In conclusion, better water quality can be achieved via photocatalytic reaction by using hybrid photocatalyst. Thus, the photocatalysis process is able to provide an effective alternative pre-treatment for seawater desalination

The Effect of Light Wavelength on Water Quality in Photocatalytic Seawater Pre-treatment

Alternative pre-treatment of seawater via photocatalytic reaction is not well explored. Although titanium oxide (TiO2) is widely used in photocatalytic reaction, the application of other material especially from biomass ash is rare. In this research, the effect of light wavelength for seawater treatment and the degradation of organic pollutants by using hybrid TiO2 photocatalyst supported by oil palm fiber ash (biomass ash) are studied. The photocatalyst which consisted of TiO2 and oil palm fiber ash weight ratio of 1:1 (i.e Ti:Ash 50:50) was synthesized via wet impregnation method. The Ti:Ash 50:50 photocatalyst was calcined at 500°C in the presence of air. The experiment was performed in a one litre borosilicate photocatalytic reactor. The percentage weight ratio of 1:400 for catalyst to seawater sample was set. The mixture of photocatalyst and water sample was stirred at 400 rpm to have homogenized distribution of the photocatalyst in the water. The investigation was carried out for two hours by exposing the reactor with either 365 nm or 420 nm mercury light. The photocatalyst was characterized by using N2 adsorption (BET) and UV/Vis/Nir to determine the specific surface area, pore volume and pore size and band gap energy of the catalyst respectively. The Ti:Ash 50:50 band gap energy was obtained at 3.1eV. This indicates that the catalyst was reactive when less than 385 nm light wavelength was used. The quality of initial and product seawater was analyzed via pH, conductivity, turbidity and chemical oxygen demand (COD). The small reduction of conductivity and COD obtained when using Ti:Ash 50:50 without light present shows the system was dominant by adsorption without no reaction. Higher reduction of conductivity, pH, turbidity and COD was achieved when the Ti:Ash 50:50 photocatalyst was exposed to 365 nm light wavelength than the Ti:Ash 50:50 photocatalyst that was exposed to 420 nm light wavelength. In addition, significant increment of water temperature (from 25°C to 100°C) was observed when 420 nm light wavelength was used. This leads to distillation dominated the process rather than photocatalytic reaction. It can be deduced that hybrid photocatalyst of Ti:Ash 50:50 has remarkable capabilities in pre-treatment and purify the seawater. The light wavelength also plays important role in adsorption behavior and photocatalytic activity of the catalyst

Effect of Calcination Temperature on Performance of Photocatalytic Reactor System for Seawater Pretreatment

Conservative desalination technology including distillation requires high energy and cost to operate. Hence, pretreatment process can be done prior to desalination to overcome energy demand and cost reduction. Objective of this research is to study the effect of calcination temperature of hybrid catalyst in photocatalytic reactor system in the seawater desalination, i.e. salt removal in the seawater. The catalyst was synthesized via wet impregnation method with 1:1 weight ratio of TiO2 and activated oil palm fiber ash (Ti:Ash). The catalyst was calcined at different temperature, i.e. 500 oC and 800 oC. The study was carried out in a one liter Borosilicate photoreactor equipped with mercury light of 365 nanometers for two hours with 400 rpm mixing and catalyst to seawater sample weight ratio of 1:400. The Chemical Oxygen Demand (COD), pH, dissolved oxygen (DO), turbidity and conductivity of the seawater were analyzed prior and after the testing. The fresh and spent catalysts were characterized via X-Ray Diffractogram (XRD and Nitrogen physisorption analysis. The calcination temperature significantly influenced the adsorption behaviour and photocatalytic activity. However, Ti:Ash which calcined at 800 oC has less photocatalytic activity. It might be because the surface of fiber ash was sintered after calcined at high temperature. The Ti:Ash catalyst that calcined at 500 oC was found to be the most effective catalyst in the desalination of seawater by reducing the salt concentration of more than 9 % compared to Ti:Ash calcined at 800 oC. It can be concluded that catalyst calcination at 500 °C has better character, performance and economically feasible catalyst for seawater desalination