Reduction of Cadmium Uptake of Rice Plants Using Soil Amendments in High Cadmium Contaminated Soil: a Pot Experiment

The aims of this study were to investigate the effect of agricultural residues on reducing cadmium uptake in rice plants. The rice plants growing on no cadmium/free cadmium soils (N), Cd soils (Cds), and Cd soils each amended with 1% w/w of coir pith (CP), coir pith modified with sodium hydroxide (CPm) and corncob (CC) under high cadmium contaminated soil with an average 145 mg Cd kg-1 soil were investigated. The results showed that the cumulative transpiration of rice grown in various treatments under high cadmium contaminated soil followed the order: Cds > CPm ≥ CP ≥ CC. These transpirations directly influenced cadmium accumulation in shoots and husks of rice plants. The CC and CP seemed to work to reduce the cadmium uptake by rice plants indicated by accumulated cadmium in the husk that were 2.47 and 7.38 mg Cd kg-1 dry weight, respectively. Overall, transpiration tended to drive cadmium accumulation in plants for rice grown in high cadmium contaminated soil. The more that plants uptake cadmium, the lower cadmium that remains in the soil

Effect of Mixture Ratio of Food Waste and Vetiver Grass on Biogas Production

The objectives of this research were to study the optimum percentage ratios of food waste and vetiver grass (Vetiveria zizaniodes (L.) Nash) for biogas production and process stability in anaerobic digestion system. The nine mixture ratios of food waste (FM) and vetiver grass (VG) were 100:0, 80:20, 75:25, 66.67:33.33, 50:50, 33.33:66.67, 25:75, 20:80 and 0:100. The biogas production was subjected to anaerobic batch with working volume of 1.8 L and had digestion time 60 d at 35 ± 2 °C. High specific methane yield of 0.30 L g-1 VS removed was obtained from the fermentation at ratio of FW:VG at 80:20 with C/N ratio of 28.20. The specific methane yield of the single digestion of food waste (100:0) and single digestion of vetiver grass (0:100) were only 0.18 and 0.11 L g-1 VS removed, respectively. It was found that the cumulative methane production of FW: VG ratio of 80:20 was increased 34.89% and 96.93% compared to single substrate of food waste and vetiver grass, respectively. The results also showed the highest COD, VS and TS removal with a percentage ratio of FW: VG at 80:20, while the single vetiver grass digestion was the lowest COD, VS and TS removal. VFAs/Total alkalinity ratio of all ratio of food waste to vetiver at digestion time 40 d remained in 0.0895±0.0007 to 0.1944±0.0027 were steadied for this digester. It can be concluded that co-digestion of food waste and vetiver improve the biogas yield and degradation efficiency

The capacity of activated kaolins to remove colour pigments from rice bran oil: the effects of acid concentration and pre-heating prior to activation

International audienceThis study focuses on the effects of both thermal treatment (between 80 and 700 degrees C) and chemical activation (concentration of sulfuric acid between 0.3 and 2 M) of natural Ranong kaolins (ground or not) from Thailand to remove the undesirable colour of rice bran oil. The mineralogical, physical and physicochemical properties of the initial and activated kaolins are discussed in relation with the bleaching effectiveness of the activated sample investigated. Generally, the greater the temperature used before the activation step and the concentration of sulfuric acid used during activation, the greater the structural degradation of the kaolinite; Al is removed from the octahedral sheet of kaolinite and amorphous SiO2 dominates the samples. The measured maximum bleaching capacity is not necessarily obtained when using the activated kaolin having the highest specific surface area and pore volume; rather, the bleaching capacity is dependent on both alumina contents and proportion of kaolinite in the samples. Indeed, the partial preservation of the kaolinite structure is crucial to obtain a good bleaching capacity of kaolin in relation to the preservation of the aluminol sites which are likely to be involved in the adsorption of unsaturated molecules present in the rice bran oil. Moreover, as previously demonstrated, a partial leaching of Al from octahedral sheets of kaolin is also an important factor in order to obtain good bleaching capacities. Finally, the optimal preheating temperature and concentration of sulfuric acid which permit the best bleaching capacity of kaolin are reported

Effect of Alumina Content and Surface Area of Acid-Activated Kaolin on Bleaching of Rice Bran Oil

This study investigated the effect of kaolin acid activation on alumina losses, surface area changes and oil bleaching performance. Ground kaolin was treated with hydrochloric or citric acid, and bleaching tests were performed on rice bran oil. The adsorption studies showed that the optimal bleaching of ~83 or ~81 % were achieved by activation with 0.5 M hydrochloric or citric acid, respectively, whereas bleaching with a commercial clay was ~82 %. The highest bleaching value was not associated with the maximum clay surface area or porosity. X-ray fluorescence showed that alumina contents of 31–34 % were suggestive for optimum bleaching depending on the different acid used. Treating ground kaolin with the same hydrochloric acid strength by varying the acid concentration and clay/acid ratio also confirmed that the best Al3+ content was ~32 %, and a value lower than one indicated the extensively destruction of kaolinite proportions leading to a decrease in its bleaching capacity, even though it had the maximum surface area. The decrease in capacity was due to the reduction of alumina content, and the parallel formation of high amorphous silica was favorable for the adsorption of anionic pigments, such as chlorophyll-a