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

Textural characteristics, surface chemistry and oxidation of activated carbon

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 nonselective 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

Fixed-bed adsorption of metal ions from aqueous solution on polyethyleneimine-impregnated palm shell activated carbon

Fixed-bed adsorption studies with virgin and polyethyleneimine (PEI)-impregnated palm shell activated carbon (AC) as a media for the removal of single Ni2+ or Cu2+ ions from aqueous solution were conducted. The studies were conducted in a vertical down flow Perspex column with influent pH at 5 with either Ni2+ or Cu2+ had an influent concentration of 1 mmol/L. The adsorption data were fitted to three-well-established fixed-bed adsorption models, namely, bed-depth-service-time (BDST), Thomas and Yoon–Nelson models. It was observed that PEI impregnation at 8.41 wt% had increased the breakthrough volume and service time of AC by factors of 2.1 (Cu2+) and 1.6 (Ni2+) as compared to virgin AC. For Cu2+ adsorption, the modelled BDST, Thomas and Yoon–Nelson curves were in very good agreement with the experimental curves while it was conversely true for Ni2+ adsorption

Recent advances in the methanol synthesis via methane reforming processes

Depleting fossil fuel resources and continuously degrading environment due to greenhouse gases demands an immediate search for alternative energy resources on an emergency basis to develop a sustainable and green environment. The utilization of coke oven gas, biogas and flue gases from fossil fuel power plants to produce synthesis gas, which is a major feedstock for the production of liquid fuels (methanol), is beneficial both from economical and environmental aspect. In this review paper, our aim is to discuss the applicability of these sources in different reforming processes to produce suitable syn-gas ratio (∼2) for methanol production. The feasibility, suitability and applicability of each source have been discussed in detail accompanied with their environmental impact and detailed economic analysis. Moreover, the influence of different supports, promoters and preparation methods on the catalyst properties to minimize carbon deposition has also been described. This review will summarize all the recent advances in the area of syn-gas production for methanol synthesis

Activity of solid catalysts for biodiesel production: A review

Heterogeneous catalysts are promising for the transesterification reaction of vegetable oils to produce biodiesel. Unlike homogeneous, heterogeneous catalysts are environmentally benign and could be operated in continuous processes. Moreover they can be reused and regenerated. However a high molar ratio of alcohol to oil, large amount of catalyst and high temperature and pressure are required when utilizing heterogeneous catalyst to produce biodiesel. In this paper, the catalytic activity of several solid base and acid catalysts, particularly metal oxides and supported metal oxides, was reviewed. Solid acid catalysts were able to do transesterification and esterification reactions simultaneously and convert oils with high amount of FFA (Free Fatty Acids). However, the reaction rate in the presence of solid base catalysts was faster. The catalyst efficiency depended on several factors such as specific surface area, pore size, pore volume and active site concentration

CO(2)/CH(4) and O(2)/N(2) kinetic selectivities of oil palm shell-based carbon molecular sieves

Carbon molecular sieves (CMS) have become an interesting area of adsorption due to their microporous nature and favourable separation factor on size and shape selectivity basis for many gaseous systems. In this work, CMS were prepared from locally available oil palm shell by thermal treatment of carbonization followed by steam activation, then benzene deposition. The carbonization of dried palm shell at 900 degrees C for 1 hr followed by steam activation at 30-420 min produced activated carbons with various degrees of burn-off. The highest micropore surface area and micropore volume of the activated samples were obtained at 53.2 burn-off. This sample was found suitable to be used as precursor for CMSs production in the deposition step. Subsequent benzene deposition onto activated samples at temperatures from 600 degrees C-900 degrees C for various benzene concentrations resulted in a series of CMS with different O(2)/N(2) and CO(2)/CH(4) kinetic selectivities

Adsorption kinetics of various gases in carbon molecular sieves (CMS) produced from palm shell

Carbon molecular sieves (CMS) have been prepared from locally available palm shell of Tenera type by a thermal treatment technique involving carbonization followed by steam activation and benzene deposition technique. Carbonization of the dried palm shells was done at 900 °C for duration of 1 h followed by steam activation at 830 °C for 30-420 min to achieve activated carbons with different degree of burn-offs. The highest micropore volume of activated carbon obtained at 53.2 burn-off was found suitable to be used as a precursor for CMS production. Subsequent benzene deposition onto activated samples at temperature range from 600 to 900 °C for various benzene concentrations have resulted in a series of CMS with different kinetic selectivities. The molecular sieving behaviour of the CMS products was assessed by kinetic adsorption isotherms of O2, N2, CO2 and CH4 at room temperature

Study on the improvement of the capacity of amine-impregnated commercial activated carbon beds for Co-2 adsorbing

Amine-based chemicals were impregnated onto activated carbon particles to improve its natural adsorption ability and selectivity to adsorb CO 2 from gas mixture stream. Characterization results achieved by measuring the surface area with ASAP 2020 showed that the amine-based chemicals blocked the mostly micropore pores of the activated carbon particles. The amine-based chemicals used in this study were, monoethanolamine (MEA) and 2-amino-2-methyl-1-propanol (AMP). The impregnation process and the subsequent blockage reduced the surface area of the activated carbon particles significantly but on the other hand enhanced the adsorption capacity and selectivity of the activated carbon for CO 2 adsorption. Elemental analysis results using energy-dispersive X-ray spectroscopy showed that the impregnation process managed to attach the reactive N 2 molecules onto the surface and inside the pores of the activated carbon particles. Images from field emission scanning electron microscope showed that due to impregnation process most of the pores of the activated carbon particles had been blocked by the MEA and AMP molecules. Sweeping exhausted non-impregnated activated carbon beds with 60ml/min pure nitrogen for 4h was enough for these beds to regain their original adsorption capacity but in contrast it was not enough to regenerate exhausted AMP, MEA-impregnated activated carbon beds to regain their original adsorption capability

Production of carbon molecular sieves from palm shell based activated carbon by pore sizes modification with benzene for methane selective separation

Palm shell based activated carbon prepared by K2CO3 activation is used as precursor in the production of carbon molecular sieve by chemical vapor deposition (CVD) method using benzene as depositing agent. The influences of deposition temperature, time, and flow rate of benzene on pore development of carbon molecular sieve (CMS) and methane (CH4) adsorption capacity were investigated. The parameters that varied are the deposition temperature range of 600 to 1000 °C, time from 5.0 to 60 min, and benzene flow rate from 3.0 to 15 mL/min. The results show that in all cases, increasing the deposition temperature, time, and flow rate of benzene result in a decrease in adsorption capacity of N2, pore volume and pore diameter of CMS. The BET surface area of CMS (approximately 1065 m2/g) and the adsorption capacity of CH4 were at a maximum value at a deposition temperature of 800 °C, time of 20 min and benzene flow rate of 6 mL/min. The product has a good selectivity for separating CH4 from carbon dioxide (CO2), nitrogen (N2), and oxygen (O2)