Showing papers by "Khairiraihanna Johari published in 2019"

Carbon Nanotubes Incorporated Z-Scheme Assembly of AgBr/TiO2 for Photocatalytic Hydrogen Production under Visible Light Irradiations.

Abstract: Photocatalytic H2 production is a promising strategy toward green energy and alternative to carbon-based fuels which are the root cause of global warming and pollution. In this study, carbon nanotubes (CNTs) incorporated Z-scheme assembly of AgBr/TiO2 was developed for photocatalytic H2 production under visible light irradiations. Synthesized photocatalysts were characterized through transmission electron microscope (TEM), X-ray photoelectron spectra (XPS), X-ray diffractometer (XRD), Fourier transform infrared (FTIR), photoluminescence spectra (PL), Brunauer Emmet-Teller(BET), and UV-vis spectroscopy analysis techniques. The composite photocatalysts exhibited a H2 production of 477 ppm which was three-folds higher than that produced by TiO2. The good performance was attributed to the strong interaction of three components and the reduced charge recombination, which was 89 and 56.3 times lower than the TiO2 and AgBr/TiO2. Furthermore, the role of surface acidic and basic groups was assessed and the photocatalytic results demonstrated the importance of surface functional groups. In addition, the composites exhibited stability and reusability for five consecutive cycles of reaction. Thus, improved performance of the photocatalyst was credited to the CNTs as an electron mediator, surface functional groups, higher surface area, enhanced charge separation and extended visible light absorption edge. This work provides new development of Z-scheme photocatalysts for sustainable H2 production.

Removal of Lead (II) Ions from Aqueous Solution Using Desiccated Coconut Waste as Low-Cost Adsorbent

Abstract: Waste from coconut milk processing industry namely desiccated coconut waste (DCW) was used to remove Pb (II) due to Pb (II) hazardous effect in the environment. The main objective of this study is to study and develop the adsorption capability of the DCW adsorbent. The chemical and physical properties of the DCW adsorbent were depicted by the FT-IR spectra and the elemental CHNS analysis. The maximum Pb (II) adsorption capacity (Q) toward DCW adsorbent was 50.33 mg/g at pH solution of 6 with the rate of 0.004 mg/min. In addition, the Pb (II) equilibrium data were best fitted to the Langmuir isotherm model, whereas the kinetic data obeyed the pseudo-second-order kinetic model. In the regeneration study, DCW adsorbent has remained stable up to two adsorption cycles. Thus, these satisfactory results revealed that the use of DCW as an alternative low-cost adsorbent for the removal Pb (II) from aqueous solution is feasible.

Enhanced elemental mercury removal by facile sulfurization of agrowaste chars

Abstract: Facile sulfurization of char from agrowaste of coconut pith (CP) and elemental sulfur was developed towards producing cheaper adsorbents for elemental mercury (Hgo) adsorption. It was found that physicochemical properties of the sulfurized chars changed with the initial CP to elemental sulfur ratio (CPS) and sulfurization temperatures, that generally affected the Hgo adsorption. The CPS ratio of 1:1 and sulfurization temperature of 300 oC (i.e. CPS300(1:1)) resulted in outstanding Hg° adsorption performance. Characterization of the char indicates the presence of the organic compounds, organic sulfur and elemental sulfur species onto the adsorbents were likely favoring the Hgo adsorption. The adsorption capacity of CPS300(1:1) was higher than 26077.7 μg/g, since the adsorbents still did not reach breakthrough time even after 80 d of adsorption process. The study on the effect of bed temperature found that the adsorbent was still effective in removing Hgo at any temperature (50 oC to 200 oC). The sulfurized-char however was non-regenerable.

A comparative study on dynamic Hg(II) and MeHg(II) removal by functionalized agrowaste adsorbent: breakthrough analysis and adsorber design

Abstract: The adsorption dynamics of inorganic mercury, Hg(II) and organic methylmercury, MeHg(II) removal by low-cost reactive agrowaste adsorbents namely CP-Pure, CP-MPTES and CP-RR was investigated in a fixed-bed adsorber. The results show that the breakthrough and saturation times were delayed with decreasing flow rate (F) and initial concentration (Co), and increasing bed height (Z). The Hg(II) possessed better adsorption performance than MeHg(II). The isotherm and kinetic model analyses of adsorption data followed the Temkin isotherm and the pseudosecond order kinetic models, respectively. The breakthrough curve was simulated well by the Thomas and Yoon-Nelson models, and then was further used for scale-up studies. The empty bed contact time (EBCT) concept was successfully demonstrated for the adsorber design and scale-up studies. The regeneration studies showed that the regenerated CP-Pure and CP-MPTES have a high regeneration efficiency up to third adsorption cycle.

Sodium dodecyl sulfate-coated-cationized agroforestry residue as adsorbent for benzene-adsorptive sequestration from aqueous solution.

Abstract: The aim of this work is to convert agroforestry residue to a novel adsorbent (M-1CTA-SDS-BT) used for adsorptive benzene sequestration from aqueous solution. In this study, the anionic surfactant-coated-cationized banana trunk was synthesized and characterized for batch adsorption of benzene from aqueous solution. The surface morphology, surface chemistry, surface area, and pore properties of the synthesized adsorbents were examined. It was proven that surface cationization successfully increased the benzene adsorption capacity of sodium dodecyl sulfate-coated adsorbents. The Langmuir isotherm model satisfactorily described the equilibrium adsorption data. The maximum benzene adsorption capacity (qmax) of 468.19 μmol/g was attained. The kinetic data followed the pseudo-second-order kinetic model in which the rate-limiting step was proven to be the film diffusion. The batch-adsorbent regeneration results indicated that the M-1CTA-SDS-BT could withstand at least five adsorption/desorption cycles without drastic adsorption capacity reduction. The findings demonstrated the adsorptive potential of agroforestry-based adsorbent as a natural and cheap material for benzene removal from contaminated water.

Supercritical Extraction of Value-Added Compounds From Empty Fruit Bunch: An Optimization Study by Response Surface Methodology

Abstract: The extraction of value-added compounds from oil palm empty fruit bunches (EFB) using supercritical CO2 (SCCD) and water as a co-solvent (modifier) was investigated. The optimization study of extraction was performed using response surface methodology with central composite rotatable design. Extraction parameters including temperature, pressure, and particle size were optimized and determined. The regression model developed gave accurate predictions and fitted well with the experimental results, yielding a coefficient of determination (R2) of 0.93. Based on the model, the optimum extraction conditions were predicted to be at 75°C, 34 MPa and particle size of 0.65–0.75 mm, with a prediction yield of 5.47%. This condition was validated by experimental runs which produced an average yield of 5.46 wt%. The supercritical extract of EFB was then characterized by GC–MS and compared with an extract obtained by Soxhlet extraction using hexane. The quantity and quality of the extract obtained by SCCD was superior to that of Soxhlet extraction.

Overview of Activity Coefficient of Methanol at Infinite Dilution in Ionic Liquids and their Modeling using Group Contribution Model

Abstract: A predictive model is developed by using a group contribution method for the estimation of the infinite dilution activity coefficient (IDAC) of methanol in ionic liquids (ILs). A simple van’t Hoff ...

Synthesis and characterization of coconut pith char adsorbents for carbon dioxide capture

Abstract: The emission of carbon dioxide (CO 2 ) from anthropogenic sources has become a public concern. Several effective and affordable post combustion CO 2 capture technology has been reported and one of the approaches is through adsorption process. This study focused the adsorption onto low-cost adsorbent that can be produced from waste biomass through carbonization method. Coconut pith (CP) was used as precursor and carbonized at temperature of 300 and 700oC under ambient condition. The chemical and physical properties showed that the surface area, pore volume, ash, moisture and carbon content of chars increased, while the yield content decreased with increasing carbonization temperatures. The char adsorbent carbonized at higher temperature (CP700) showed the better performance with CO 2 adsorption capacity of 10.00 mmol/g at 25oC. It was revealed that carbonization temperature greatly affects the properties of CP, hence influence the ability of the adsorbent to capture the CO 2 . Hence, these unique properties and adsorption performance showed that char adsorbent enable to be used as an effective adsorbent for CO 2 capture and thus improving environmental quality and sustainability.

Absorbents, Media, and Reagents for Carbon Dioxide Capture and Utilization

Abstract: In the last few decades, climate change phenomena namely floods, droughts, and cyclones commonly appeared in the news headlines. These phenomena were mainly driven by global warming. Anthropogenic emissions of carbon dioxide resulted in its accumulation in the atmosphere which enhanced the greenhouse effect. Carbon dioxide capture and utilization was introduced as a method to mitigate the effects of global warming. Absorption is currently the most well-established type of technology available in the market. Different types of solvent reported as absorbents for carbon dioxide capture along with media and reagents for utilization process were reviewed. Among all the absorbents, amine solution was the most widely reported type of absorbent. Despite its effectiveness in capturing carbon dioxide, amine solution has some disadvantages such as high volatility, low thermal stability, and high oxidation degradation. Emerging solvents such as ionic liquid, amino acid salt, and weak base were suggested as alternative solvents for carbon dioxide capture. For carbon dioxide conversion process, metal ions and organic reagents were added into carbon dioxide-saturated absorbents to convert carbon dioxide into value-added products at relatively lower temperature and pressure compared to conventional utilization process. This reduces the energy requirement during carbon dioxide capture and utilization process.