Wan Mohd Ashri Wan Daud

The effects of carbonization temperature on pore development in palm-shell-based activated carbon

A series of experiments have been conducted to study the effects of carbonization temperature on pore development in palm shell activated carbon. Activation of char prepared at 500, 800 and 900°C was performed at 820°C in a fluidized bed reactor. Activated carbon prepared from high temperature char had a significant amount of micropore volume. For all carbonization temperatures investigated, both micropore and macropore volumes showed maximum values at intermediate carbon burn-off. Only a small amount of mesopore was developed in the initial stage of activation. However, as the level of burn-off increased, a rapid development in mesopore was observed. No clear pattern was demonstrated on the effects of carbonization temperature on the development of mesopore and macropore volumes.

Hexavalent chromium adsorption on impregnated palm shell activated carbon with polyethyleneimine.

Removal of Cr(VI) ions from aqueous solution was investigated using modified palm shell activated carbon. Low Molecular Weight Polyethyleneimine (LMW PEI) was used for impregnation purpose. The maximum amount of LMW PEI adsorbed on activated carbon was determined to be approximately 228.2mg/g carbon. The adsorption experiments were carried out in a batch system using potassium dichromate K(2)Cr(2)O(7) as the source of Cr(VI) in the synthetic waste water and modified palm shell activated carbon as the adsorbent. The effects of pH, concentration of Cr(VI) and PEI loaded on activated carbon were studied. The adsorption data were found to fit well with the Freundlich isotherm model. This modified Palm shell activated carbon showed high adsorption capacity for chromium ions.

Textural characteristics, surface chemistry and oxidation of activated carbon

Abstract Numerous researches were reviewed and interpreted to depict a comprehensive illustration of activated carbon and its behavior towards oxidation. Activated carbon as one of the most important adsorbents is tried to be described in this review paper by terms of its “Textural Characteristics” and “Surface Chemistry”. These two terms, coupled with each other, are responsible for behavior of activated carbon in adsorption processes and in catalytic applications. Although as-prepared activated carbons are usually non-selective and their surfaces suffer from lack of enough reactive groups, their different aspects may be improved and developed by diverse types of modifications. Oxidation is one of the most conventional modifications used for activated carbons. It may be used as a final modification or as a pre-modification followed by further treatment. In this paper, methods of oxidation of activated carbon and other graphene-layer carbon materials are introduced and wet oxidation as an extensively-used category of oxidation is discussed in more detail.

A review on advances in photocatalysts towards CO2 conversion

The present situation reveals the dependence on fossil fuels, which is seriously accountable for two major impediments: (i) global warming due to increasing atmospheric carbon dioxide (CO2) and (ii) the alarming consumption of energy assets. The reduction of green CO2 in terms of producing solar fuels would be an expedient accomplishment to resolve both problems, simultaneously. The review classifies different categories of photocatalysts applied in foregoing photocatalytic CO2 conversion processes with detailed information concerning operating conditions, preparation techniques and physical properties of catalysts, radiation sources, and selectivity. The categories are concentrated on metal oxides, sulfides, phosphides, and p-type and nonmetal oxide semiconductors. In addition, their modification by doping co-metals, noble metals, transition metals and non-metals for visible light response is emphasized. Besides, for harnessing solar fuel, the recent prospect and advancement of novel sensitized catalysts by dye elements, phthalocyanines and quantum dots (QDs) are also highlighted in this review. This technology needs more efficient solar active catalysts to increase production rates as well as selectivity. The recent scenario indicates that massive prospects and opportunities still exist in this area for further investigation on catalyst selection.

Recent advances and prospects of catalytic advanced oxidation process in treating textile effluents

Abstract In the past few years, there have been many researches on the use of different types of homogenous catalyst for the degradation of textile wastewater in conventional advanced oxidation processes (AOPs). However, homogenous AOPs suffer from few limitations, including large consumption of chemicals, acidic pH, high cost of hydrogen peroxide, generation of iron sludge, and necessity of post-treatment. Therefore, recently, there have been more researches that focus on improving the performance of conventional AOPs using heterogeneous catalysts such as titanium dioxide, nanomaterials, metal oxides, zeolite, hematite, goethite, magnetite, and activated carbon (AC). Besides, different supports such as AC that have been incorporated with transition metals and clays have been proven to have excellent catalytic activity in AOPs. This paper presents a comprehensive review of advances and prospects of catalytic AOPs for the decontamination of a wide range of synthetic and real textile wastewater. This review provides an up-to-date critical review of the information on the degradation of various textile dyes by a wide range of heterogeneous catalysts and adsorbents. The future challenges of AOPs, including chemical consumption, toxicity assessment, reactor design, and limitation of catalysts, are discussed in this paper. In addition, this paper also discusses the presence of ions, generation of by-products, and industrial applications of AOPs. Special emphasis is given to recent studies and large-scale combination of AOPs for wastewater treatment. This review paper concludes that more studies are needed for the kinetics, reactor design, and modeling of hybrid AOPs and the production of their corresponding intermediate products and secondary pollutants. A better economic model should also be developed to predict the cost of AOPs, as the treatment cost varies with dyes and textile effluents.

Heterogeneous catalysts for advanced bio-fuel production through catalytic biomass pyrolysis vapor upgrading: a review

Nowadays concerns regarding fossil fuel resources depletion as well as environmental issues attributed to CO2 accumulation in the atmosphere force communities toward utilizing biomass as a substitute fuel source which is environmentally secure and renewable. Pyrolysis bio-oil from biomass comprises varieties of undesirable oxygenate and heavy compounds and has to be treated before feeding to bio-refineries. Catalytic biomass pyrolysis vapor upgrading presently seems to be a techno-economical process toward production of fuel-like components. However, selection of stable and productive catalyst(s) to yield desirable chemicals with low coke formation is a great challenge. The three most important classes of catalysts comprising microporous zeolites, mesoporous catalysts and metal based catalysts are utilized for vapor phase bio-oil upgrading. This study offers a comprehensive review on catalytic biomass pyrolysis vapor upgrading by emphasizing particularly on catalyst types and properties, coke formation over catalysts and catalytic process conditions.

A Comparison of Central Composite Design and Taguchi Method for Optimizing Fenton Process

In the present study, a comparison of central composite design (CCD) and Taguchi method was established for Fenton oxidation. [Dye]ini, Dye : Fe+2, H2O2 : Fe+2, and pH were identified control variables while COD and decolorization efficiency were selected responses. L 9 orthogonal array and face-centered CCD were used for the experimental design. Maximum 99% decolorization and 80% COD removal efficiency were obtained under optimum conditions. R squared values of 0.97 and 0.95 for CCD and Taguchi method, respectively, indicate that both models are statistically significant and are in well agreement with each other. Furthermore, Prob > F less than 0.0500 and ANOVA results indicate the good fitting of selected model with experimental results. Nevertheless, possibility of ranking of input variables in terms of percent contribution to the response value has made Taguchi method a suitable approach for scrutinizing the operating parameters. For present case, pH with percent contribution of 87.62% and 66.2% was ranked as the most contributing and significant factor. This finding of Taguchi method was also verified by 3D contour plots of CCD. Therefore, from this comparative study, it is concluded that Taguchi method with 9 experimental runs and simple interaction plots is a suitable alternative to CCD for several chemical engineering applications.

Effects of pyrolysis parameters on hydrogen formations from biomass: a review

This study investigates the effects of different parameters such as biomass composition, moisture content, particle size, heating rate, temperature, inert gas, reactor system, and catalyst on the production of hydrogen gas (HG) and other gases (OGs) such as CO2, CO, CH4, C2H6, and so on. The reformation of OGs into H2 via the shift reaction significantly increases the total HG formation during biomass pyrolysis. Biomass raw material is capable of producing different proportions of HG at different temperatures because the raw material structure varies from one material to another. It is very puzzling that the formation of HG and total gas (TG) could either increase or decrease with moisture and this result varied between researchers. Smaller particles are more suitable than larger ones in terms of HG and TG formation. Additionally, longer residence times and higher temperatures favor good HG yield while the heating rate is a function of heat flux and particle size of biomass fuel is supposed to increase the pyrolytic gases and properties. Moreover, the heating rate would play a smaller role on the process when the system is introduced with inert gas and if the purpose is to maximize the production of TGs, secondary reactions such as thermal cracking, re-polymerization, and re-condensation should be maximized because the inert gas removes the volatiles from the pyrolysis environment. Therefore, the ultimate product of biomass conversion is dependent on the reactor design and type of feedstock in the presence of appropriate catalysts.

Catalytic hydrogenation of phenol, cresol and guaiacol over physically mixed catalysts of Pd/C and zeolite solid acids

Highly reactive phenolic compounds of pyrolysis bio-oil are recognized as a major cause of the unpleasant properties of this biofuel. Catalytic hydrodeoxygenation of phenolic compounds of bio-oil is an efficient technique for improving the quality of bio-oil. Dual function catalysts consisting of metal and acid sites are usually used for transformation of bio-oil/bio-oil model compounds to high value hydrocarbons. Metal and acid sites are generally involved in hydrogenation/hydrodeoxygenation and dehydration/hydrocracking/dealkylation/alkylation reaction mechanisms, respectively. In this work, the product selectivity of hydrogenation of phenol, o-cresol, m-cresol and guaiacol was investigated over combined catalysts of Pd/C with zeolite solid acids of HZSM-5 (Si/Al of 30, 50 and 80) and HY (Si/Al of 30 and 60). Catalytic activity and product distribution in the hydrogenation process were affected by the density and strength of zeolite acid sites. HZSM-5 (30) with only weak acid sites showed lower cyclohexane selectivity compared with HZSM-5 (50) and HZSM-5 (80) which had both weak and strong acid sites. HY (30) and HY (60) containing only strong acid sites favored production of cycloketones.

Exploring Potential Methods for Anchoring Amine Groups on the Surface of Activated Carbon for CO2 Adsorption

Activated carbon can be effectively modified for CO2 adsorption with amine groups due to their high affinity for CO2. Using approaches such as impregnation, some modifiers containing amine groups are physically adsorbed on the surface of carbon, whereas other amine groups can be directly or indirectly chemically bound to the activated carbon matrix. In the context of exploring potential techniques for grafting amine groups onto activated carbon surfaces, we herein review the literature on modifications applied to different materials and supports for a variety of applications, limited to neither activated carbon nor CO2-adsorption applications. We focus on the processes of grafting amine groups and the parameters influencing these processes. Moreover, the mechanism of CO2 adsorption involving amine groups is discussed.