Rice husk (RH) is an agricultural waste which has been utilized as useful renewable resources to produce energy with high-purity silica (SiO2) contents. With such a large availability of rice husk, it becomes economical to industrial applications. This paper was study about the removal of iron from rice husk in aqueous citric acid by using acid leaching treatment. The parameters chosen were reaction temperature, stirring speed, acid concentration and stirring time. The optimum conditions for the maximum removal of 0.14% of iron with citric acid leaching treatment were observed at solution temperature of 70°C; thermostat magnetic stirrer hotplate, 150 W; acid concentration 0.1M-1.0M; stirring time 6h-12h. This method resulted the removal efficiency of iron increasing considerably with the increasing leach C2H7O8 acid concentration. The optimization of the process conditions of the citric acid leaching treatment under the optimum conditions with 6h of stirring time and acid concentration of 1.0M were conducted to remove the metallic impurities of Fe from husks and shows remarkable result.

This study investigated the effects of adding titanium dioxide (TiO2) and aluminium oxide (Al2O3) nanoparticles into Sn3.0Ag0.5Cu (SAC) lead-free solder alloy on the thermal properties and wettability. In comparison with SAC lead-free solder without addition of nanoparticles, the melting temperature is very similar and comparable. The solidus temperature is in the range of 217.1 to 217.2 °C with the addition of TiO2 and Al2O3 nanoparticles. The results shows that the addition of 0.25-1.0 wt% of TiO2 and Al2O3 nanoparticles caused the liquidus temperature to decrease from 222.4 to 220.5 °C. The spreading area of SAC-xTiO2-xAl2O3 lead-free solder increases from 5.7 to 7.1mm at 0-0.5wt% of TiO2 and Al2O3 nanoparticles. The contact angle decreased from 66.09° to 46.84° when the composition of TiO2 and Al2O3 increases from 0-0.5wt%.

Rice husks (RH) are agricultural wastes available abundantly in rice producing country. A by-product obtained from combustion of rice husk is rice husk ash (RHA) which is rich in silica (SiO2) contents. This paper focused on the effect of acid leaching treatment on rice husk to produce high-purity silica. There are 4 different states of conditions involved; raw rice husk (RRH), treated rice husk (TRH), rice husk ash (RHA), and treated rice husk ash (TRHA). Citric acid; C6H8O7 was used as a leaching agent. TRH and TRHA was leached to see whether treated rice husk before combustion (TRH) or treated rice husk after combustion (TRHA) will produce more high-purity silica. Chemical composition analysis shows high amorphous silica content which is 98.47% with low metallic impurities at 1.0M C6H8O7, 70 oC for treated rice husk (TRH). X-ray diffraction (XRD) pattern shows the presence of amorphous silica in treated rice husk (TRH) and crystalline silica in treated rice husk ash (TRHA). Fragmentation of TRH into small pieces after acid leaching is seen where there is significant increase in the exposed surface areas. High-purity amorphous silica with more than 98% was prepared via citric acid leaching treatment and combustion process.