The effect combination of acid treatments for silicon carbide (SiC) production from rice straw
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Rice straw is an abundant and low cost agricultural waste with is locally available. On the basis of this study, it is concluded that 96.45 % silicon carbide pre-cursor can be produced by the process of pyrolysis of rice straw at 1100 ºC with a holding time of 82.65 minutes and a flow rate of 2.00 L/min nitrogen. The SiC pre-cursor was produced without additional catalyst process, thus which can reduce the cost of the product. The most significant parameter that contributes to the highest yield of SiC pre-cursor is the holding time and the nitrogen flowrate. This outcome is important because of the short pyrolysis time and at low temperature will result in reduced manufacturing costs. The rice straw itself have a high percentage of inorganic compound material; which is SiO2, SO3, K2O, CaO, TiO2, MnO, Fe2O3, CuO, ZnO, Cl compared to the other acid treated samples and consecutive acid treated (CATS) samples. With the removal some of the inorganic compound such as ZnO and CuO will increase the percentage of the SiO2 produced. In the HCl acid treated samples which are a commonly used acid for the SiC production produce only SiO2 at 54.3 % compared to other treatments. In the H2SO4 acid treated samples, the SiO2 yield is at 65.8 % which is higher than HCl sample which can be believed it can be the choice of impurities removal but when compared to the citric acid (C6H8O7) the efficiency of sulphuric acid (H2SO4) are low because in the C6H8O7 the SiO2 percentage is the highest which is at 81 % but have the highest percentage of 2.98% Fe2O3. The Fe2O3 is an unwanted inorganic compound because the Fe2O3 can inhibit the process of SiC production thus, resulting the lower production value and SiO2. The consecutive acid treatment giving the essential result to produce SiC which is having the lowest value of Fe2O3 and also eliminate the ZnO and CuO and the C6H8O7 acid treated sample can be the second option to produce the SiC respectively. Regarding to leaching process it was found that acid treatment helped to reduce the level of inorganic compound, leading to higher purity of raw material with porous structure as confirm in FTIR analysis. The characterization results showed the possibility for production of silicon carbide with well-developed whiskers and crystal structure from rice straw by pyrolysis process in this experiment. With these it confirms that the CATS have a higher potential in SiC production with purity were found to be comparable to a moissanite -3C and acceptable in the market.