Reducing Heavy Metal Element from Coal Bottom Ash by Using Citric Acid Leaching Treatment

Coal ash is the residue that is produced during coal combustion for instance fly ash, bottom ash or boiler slag which was primarily produced from the combustion of coal. With growth in coal burning power station, huge amount of coal bottom ash (CBA) considered as hazardous material which are normally disposed in an on-site disposal system without any commercialization purpose. Previous researchers have studied the extraction of silica from agricultural wastes such as palm ash and rice husk ash (RHA) and CBA by using leaching treatment method. In this study, the weaker acid, citric acid solution was used to replace the strong acid in leaching treatment process. Result showed that the heavy metal content such as Copper (Cu), Zinc (Zn) and Lead (Pb) can be decrease. Meanwhile the silica can be extracted up to 44% from coal bottom ash using citric acid leaching treatment under the optimum reaction time of 60 minutes with solution temperature of 60°C and concentration of citric acid more than 2%

Evaluation of some important physicochemical properties of starch free grewia gum

Gums obtained by extraction from the inner bark of stems can be found in association with starch, which must be digested in order to obtain a refined polysaccharide isolate. In the present study, grewia gum obtained from the inner bark of the stems of Grewia mollis was shown to co-exist with starch and the effect of starch digestion on the physicochemical properties of the resultant polysaccharide was evaluated. The gum was extracted by maceration of the inner bark in deionized water and isolated by a combination of filtration, centrifugation and finally precipitation with absolute ethanol to produce the crude grewia gum extract (GG). The presence and content of starch in the gum sample was determined followed by enzymatic digestion of the starch using α-amylase (Termamyl 120L) to give a starch-free extract (GGDS). Physicochemical properties of the extracts such as total carbohydrates, total protein, differential sugar composition, NMR, intrinsic viscosity and rheological behaviour of the samples were evaluated. The GG extract had total carbohydrate content of ∼ 60 % out of which 11.8 % was starch, and a protein content of 2.3 %. Samples also contained galacturonic and glucuronic acid which were highly acetylated. Both samples had a higher proportion of galacturonic acid than glucuronic acid and contained rhamnose, arabinose, galactose, glucose and xylose as neutral sugars in varying proportions. Rheological measurements on 2 %w/w dispersions of the extracts show minor differences between both the original extract and the de-starched material but were influenced by changes in pH

New Natural Injection-Moldable Composite Material from Sunflower Oil Cake

Through a twin-screw extrusion process the native structure of sunflower oil cake was completely transformed (globular protein denaturation/texturization and husk fiber defibration) into a simpler matrix-fiber structure, as could be seen on SEM micrographs. Further chemical reduction of protein disulfide bridges greatly reduced the melt viscosity of the moistened composite that it could be injection-molded. The molded specimens were tested and their tensile and flexural properties and water absorption calculated. Their water resistance appeared to be particularly high, and could be enhanced further after a thermal treatment (N2, 200°C). The proteic matrix seemed to behave like a natural thermoset resin. Sunflower oil cake could be used without any additives to make biodegradable, water resistant and exceptionally cheap material

Valorisation of rice husks using a TORBED® combustion process

World production of rice exceeds 750 million tonnes per year of which a fifth is removed in the form of rice husk during the milling process. The use of rice husks as a source of sustainable and renewable energy is often hindered by lack of capital and a poor understanding of rice husk combustion characteristics. This results in the selection of poor quality technology which generates significant quantities of harmful crystalline silica waste. Despite previous work in the area, detailed characterisation of the combustion of rice husk ash in a TORBED reactor across a wide temperature range has not yet been attempted and little effort has been directed towards assessing the economic viability of generating quality rice husk ashes. The use of a TORBED reactor enables low residual carbon after combustion without the generation of harmful crystalline material. Rice husk was combusted in a 400 mm reactor at temperatures between 700 and 950 °C. In the subsequent characterisation studies the resulting materials were shown to be fully amorphous high purity silica (> 95%) and were readily digested in a series of alkaline digestion experiments. Complete silica conversion was only possible using uneconomic Na₂O/SiO₂ ratios and further optimisation of the combustion process to generate higher surface area material is necessary to increase the digestion rates further. Provisional economic analysis suggests that sales of the by-product enhance the returns from rice husk based power generation. TORBED reactors enable the combustion of rice husk with considerable operating flexibility and they generate products that could be used to displace resource intensive products and processes thus, added value from the by-products can be obtained by using TORBED reactor technology