Research On The Safe Utilization Technology Of Cadmium Exceeding Stand Rice Resource

This study was aimed at the safe use of cadmium exceeding stand rice resource in southern indica rice.Using fast and safe physical polishing reduces cadmium,histological analysis of rice and rice husk pretreatment technique,we studied the optimum process parameters of browning and decreasing cadmium in brown rice,effect of grain structure on grinding and cadmium reduction and optimum process parameters of rice husk pretreatment for preparing high-purity amorphous SiO₂.The studies have shown that the existing millet mechanical grinding is an effective method for reducing cadmium in excessive cadmium rice.However,the existing grinding machinery has limitations.The distribution of cadmium and other components in rice grains and the structure characteristics of rice grains have a great influence on the efficiency of grinding and lowering cadmium.Using the ultrasonic-assisted treatment technique,it was found that concentration of citric acid is reduced to 1/10,the equivalent removal efficiency of rice husk alkali metal,heavy metal,and other soluble impurities can be achieved or better.These results provide a scientific basis for the safe use of cadmium exceeding stand rice resources in southern indica rice varieties,and they have industrial application prospects,which are of great significance to the development of rice cadmium reduction technology,deep processing technology and variety breeding.The main conclusions of this study were as follows:1.Using existing polished rice machine,it was found that the total grinding rate is less than 19%,the cadmium reduction efficiency is 2 times,and the impact on the whole rice rate is small.The optimum polishing process parameters for the optimum average flow rate,single polishing degree,and unit weight reduction efficiency are 11.6 kg/min/L,3.3,363.0 g/min/L for the short-grain type and 11.0 kg/min/L,2.3,226.4 g/min/L for the long-grained types,respectively.2.The grain structure of rice is significantly different for different breeds and growing environments.The three-dimensional size and moisture content of rice are important factors affecting the grinding efficiency.The structure of rice grains can be roughly divided into four types:annual ring type,hamburger type,gradual type,and mosaic type.The components of cadmium,starch,and protein in rice grains are non-homogeneous distributed.Preliminary exploration shows that scanning electron microscopy-X-ray energy spectroscopy?SEM-EDS?quantitative analysis technology is a method that can quickly obtain the element distribution characteristics in rice grains.3.There was no significant difference the removal efficiency of impurities in rice husk with citric acid,sulfuric acid and hydrochloric acid,citric acid and sulfuric acid could take higher treatment temperatures,but the temperature of hydrochloric acid treatment should not be higher than 60°C.The optimal process parameters of citric acid-ultrasonic assisted method were as follow:0.5%for citric acid concentration,500 W for ultrasonic power,30 min for treatment time,80?for temperature,and 1 rinse.The amorphous rice husk SiO₂ obtained through the combustion at 1000°C has a high purity of 99.2%.