An efficient plasmonic photovoltaic structure using silicon strip-loaded geometry

We show that a silicon thin-film photovoltaic structure with silicon strips on the top and grooves on the silver back contact layer can absorb incident solar energy over a broad spectral range. The silicon strips on the top scatter the incident light and significantly help couple to the photonic modes in the smaller wavelength range. The grooves on the silver back contact layer both scatter the incident light and help couple to the photonic modes and resonant surface plasmon polaritons. We find an increase of ∼46% in total integrated solar absorption in the proposed strip-loaded structure compared to that in a planar thin film structure of same dimensions. The proposed structure offers simpler fabrication compared to similar plasmonic-inspired designs

Sulfur and nitrogen removal of model fuel using activated carbon derived from oil palm shell

This research was done to understand the suitability and effectiveness of oil palm shells (OPS) as low cost adsorbents via physically activation with carbon dioxide (CO2) as an adsorbent for desulphurization and denitrogenation of a model fuel under different concentration. Batch mode experiments were conducted to study the effects concentration of Benzothiophine, Quinoline and Indole. Activated carbon (AC) was prepared at three different activation temperatures (500°C, 600°C, and 700°C), which was characterized with Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (mR), and a mercury intrusion porosimeter. After adsorption, the solution was analysed with a Gas Chromatography (GC). Equilibrium adsorption isotherms and kinetics were investigated. The experimental data were analysed by the Langmuir and Freundlich models of adsorption. The adsorption isotherm data were fitted well to Langmuir isotherm and the most adsorption capacity on the best suited AC for Benzothiophene, Quinoline, and Indole were 3.64 mg/g, 4.19 mg/g and 2.98 mg/g respectively. The rates of adsorption were 0.19409 h-1, 0.08411 h-1, and 0.02883 h-1 for the adsorption of Benzothiophene, Quinoline, and Indole respectively. The kinetic data obtained at different concentrations have been analysed using a pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The pseudo-first­order model best described the sorption process and was employed in predicting the rate constant, equilibrium sorption capacity as well

Recovery and characterization of used lubricating oil using acid with two different adsorbents

This study is a form of experimental analysis that utilizes used lubricating oil (ULO) in order to reclaim base oil by using a combination of acetic acid and two different adsorbents namely aluminum oxide (Al2O3) and river sand (RS). The two different adsorbents were used to compare for better quality of oil using the same method. The characterization of the recovered ULO samples was conducted by using Fourier-transform infrared spectroscopy (FTIR) and the viscosity was tested by using the viscometer. Based on the results obtained, the Al2O3 seems to be a better adsorbent than RS in several tests such as density, sludge removal and viscosity. For better viscosity and mass of sludge values, the Al2O3 adsorbent is more suitable compared to the RS. It was found that by using Al2O3, there is a 26% viscosity reduction for ULO samples. By using RS, 6.67% viscosity reduction was found for ULO samples. 24.9% and 25.7% of sludge removal was found in ULO samples by Al2O3 and RS, respectively. FTIR analysis showed that before treatment oxidative compounds such as alkens and helides were present in the ULO and UEO samples. However, after treatment by both of the adsorbents, the oxidative compounds were removed. The removal of the alkenes and alkyl halides has evidently indicated the treatment was able to remove the oxidative compounds in the oil

Removal of Nitrogen containing compounds from fuel using modified activated carbon

This study was carried out to understand the suitability of activated carbon (AC) which is modified with hydrochloric acid (HCl) and tested by its adsorption capacity of nitrogen containing compounds (NCC) from fuel with three variables such as different concentrations of model fuel, contact time, and amount of modified AC (MAC). Batch mode experiments were conducted to remove quinoline (QUI) and indole (IND) from the model fuel prepared from n-hexane. All the experimental data were analysed using ultraviolet-visible spectroscopy after adsorption experiment between adsorbent and model fuel. Modification of commercial AC involved impregnation with different ratios of HCl solution. The characterization of modified and unmodified AC was done by using fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM). The adsorption potential of the MAC was measured based on the two isotherms, which are Langmuir and Freundlich isotherms to determine the isotherm constants and two kinetic models which are pseudo-first order and pseudo-second order. The adsorption capacity for QUI and IND was found to be 0.4708 mg/g and 0.8094 mg/g, respectively. On the other hand, the rate of adsorption for QUI and IND was 6.3766 and 0.4992, respectively. The adsorption kinetic experiment for both QUI and IND was found to follow the pseudo first-order

Removal of chlorinated phenol from aqueous solution utilizing activated carbon derived from papaya (carica papaya) seeds

Activated carbons (ACs) were prepared from papaya seeds with different dry weight impregnation ratios of zinc chloride (ZnCl2) to papaya seeds by using a two-stage self-generated atmosphere method. The papaya seeds were first semi-carbonized in a muffle furnace at 300 oC for 1 h and then impregnated with ZnCl2 before activation at 500 oC for 2 h. Several physical and chemical characteristics such as moisture, ash, pH, functional groups, morphological structure and porosity of prepared ACs were studied and presented here. AC2, with the impregnation ration of 1 : 2 (papaya seeds: ZnCl2), yielded a product that had the highest adsorption capacity, 91.75%, achieved after 180min contact time. The maximum Brunauer, Emmett and Teller (BET) surface area of AC2 was 546m2/g. Adsorption studies indicated that AC2 complied well with the Langmuir isotherm (qm=39.683mg g-1) and the pseudo-second-order (qe=29.36mg g-1). This indicated that chemisorption was the primary adsorption method for AC2. The intraparticle diffusion model proved that the mechanism of adsorption was separated into two stages: the instantaneous stage and the gradual adsorption stage. Overall, this work demonstrated the suitability of using papaya seeds as a precursor to manufacture activated carbon

Optimization and activation of renewable durian husk for biosorption of lead (II) from a aqueous medium

Background: Biosorption of lead Pb(II) by durian husk activated carbon (DHAC) was investigated. The main aim of this work is to explore the effect of operating variables such as pH, biosorbent dose, temperature, initial metal ion concentration and contact time on the removal of Pb(II) from synthesized aqueous medium using a response surface methodology (RSM) technique. The experimentation was performed in two sets, namely set 1 and set 2. Results: For experimental set 1, pH was set to 7.0. The optimum conditions for the remaining parameters were determined to be 0.39 g DHAC dose, 60 min contact time and 100 mg L−1 of initial metal ion concentration, which yielded maximum biosorption capacity of 14.6 mg g−1. For experimental set 2, 41.27 °C, 8.95 and 99.96 mg L−1 were the optimum conditions determined for temperature, pH and initial Pb(II) concentration, respectively; which revealed a maximum adsorption capacity of 9.67 mg g−1. Characterization of the adsorbent revealed active functional groups such as hydroxyl, carboxylic, alcohol and hemicellulose. The equilibrium adsorption data obeyed the Langmuir isotherm and pseudo‐second‐order kinetic models with maximum Langmuir uptake of 36.1 mg g−1. Conclusions: The biosorbent was capable of reuse, so that the abundant durian husk could be utilized effectively for the removal of Pb(II) from polluted water

Properties tuning of palm kernel shell biochar granular activated carbon using response surface methodology for removal of methylene blue

This study aimed to produce palm kernel shell granular activated carbon (PKSGAC) from slow vacuum pyrolysed PKS biochar (PKSB) via chemical activation using a horizontal tubular split zone furnace. The study also investigated the effects of varying parameters of the PKSGAC on its colour removal ability. The PKSB was activated through chemical activation using potassium hydroxide (KOH) at various parameters such as activation temperature (700oC to 850oC), KOH concentration (50 % w/v to 100 % w/v) and particle size of PKSB (0.4 mm to 2.5 mm). The novelty of this work lies in the study of chemical activation on various particle size ranges using response surface methodology (RSM) to model the relationships between various parameters. The PKSB was characterized to determine its thermal condition, and the PKSGAC was characterized to determine the iodine number, bulk density, ash content, moisture content, surface area and morphology structure. The parameters that were used for each sample were determined by using the RSM based on central composite design (CCD). In this study, design expert version 11.0 software was used and three parameters as independent variables were manipulated. Finally, three different PKSGAC samples of different particle sizes were used to test for the methylene blue (MB) dye removal with the concentration of 5 mg/l, 10 mg/l, 15 mg/l and 20 mg/l. Thermal analysis showed that the total weight loss of the PKSB sample was 58.30% and for PKSGAC the range of the product yield as shown from the RSM was from 33.23% to 96.33%. The RSM also showed that the values for moisture content were in a range from 0% - 39%, as for the ash content value from 2% - 12%, while for the bulk density ranged from 0.17 g/cm3 - 0.50 g/cm3. The highest iodine value achieved was 1320 mg/g at activation temperature of 850oC, KOH concentration of 50% w/v and particle size of 0.4 mm. From the RSM, an iodine number of 1100 mg/g could be obtained using an activation temperature of 850oC, the KOH concentration of 69.22% w/v and the particle size of 0.59 mm. From the BET analysis, the PKSGAC sample obtained 581 m2/g for SBET and 0.3173 cm3/g for the Vtot. The highest percentage dye removal of MB dye was 89.61% to 97.63% at 775oC activation temperature, 75% w/v KOH concentration and 0.4 mm particle size. This work produced RSM models to predict the relationships between the parameters and the response, as well as the performance on MB dye removal

A proposal and a theoretical analysis of an enhanced surface plasmon coupled emission structure for single molecule detection

We propose a structure that can be used for enhanced single molecule detection using surface plasmon coupled emission (SPCE). In the proposed structure, instead of a single metal layer on the glass prism of a typical SPCE structure for fluorescence microscopy, a metal-dielectric-metal structure is used. We theoretically show that the proposed structure significantly decreases the excitation volume of the fluorescently labeled sample, and simultaneously increases the peak SPCE intensity and SPCE power. Therefore, the signal-to-noise ratio and sensitivity of an SPCE based fluorescence microscopy system can be significantly increased using the proposed structure, which will be helpful for enhanced single molecule detection, especially, in a less pure biological sample

Development of carbon dioxide adsorbent from rice husk char

This study was mainly concerned about the development of carbon dioxide (CO2) adsorbent from rice husk (RH). Several chemical treatments were used to produce activated rice husk char (RHAC) from RH. Initially the RH was refluxed with 3M of sodium hydroxide (NaOH) solution, activation followed by using 0.5M of zinc chloride (ZnCl2) solution and finally acidic treatment by using 0.1M of hydrochloric acid (HCl). Then, the RHAC was functionalized by using 3-chloropropylamine hydrochloride (3-CPA) and noted as RHN. RHN samples were characterized with scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), fourier transform infrared spectroscopy (FTIR). Based on the SEM, the RHN sample had a large pore diameter compared to RH sample after being treated. Based on MIP data, the average pore diameter between RH and RHAC samples were increased significantly from 0.928 microns to 1.017 microns. The RHN sample also had higher total porosity (%) compared to RHAC and RH (58.45%, 47.82% and 45.57% respectively). The total specific surface area of the sample was much increasing from RHO to RHAC (29.17 m2/g and 62.94 m2/g respectively) and slightly being decreasing from RHAC to RHN (58.88 m2/g). FTIR result showed the present of weak band at 1587 cm-1 which demonstrating of the amine group present on the sample. The CO2 capture result showed that the decreasing of operating temperature can increase the breakthrough time of CO2 capture. On the contrary decreasing of CO2 gas flow rate can increase the breakthrough time of CO2 capture. The highest total amount of CO2 adsorbed was 25338.57 mg of CO2/g of RHN sample by using 100 mL/min of gas flow rate at 30oC. Based on adsorption isotherm analysis, the Freundlich isotherm was the best isotherm to describe the CO2 adsorption on the sample

Adsorptive denitrogenation of fuel by oil palm shells as low cost adsorbents

This study reviews the suitability and effectiveness of oil palm shells as low cost adsorbents via physically activation with carbon dioxide as an adsorbent for denitrogenation of fuel under different concentrations. With hydrogen, high temperature and pressure, hydro-denitrogenation (HDN) is used to remove Nitrogen Containing Compounds (NCCs). However, the cost of HDN is increasing rapidly due to the increasing concentration of NCCs in fossil fuels. NCCs compete with sulfur compounds on the active sites of catalysts in the conventional process. Therefore, NCCs should be removed as much as possible. Thus, searching for an alternative process to remove NCCs in a cost efficient manner is very important