Study On Synthesis And Properties Of Rice Husk-based Heavy Metal Efficient Adsorbent

Rice is an important food in most countries all over the world. As such, the growing population of the world need to continue production of rice on a steady basis. According to the statistics of U.S. Department of Agriculture, the world consumed 470 million metric ton of rice in recent years. Meanwhile, it also produced several million tons of corresponding rice husk. In particular, a large agricultural country in Asia, such as China and India, resulting in a large quantity of rice husk. Rice husk as a kind of rich and low cost renewable biomass resources, within this context, how to achieve its efficient conversion and utilization, which will play a very important role to meet the demands of the increasingly serious environmental issues and energy crisis. In this paper, agricultural waste i.e. rice husk was used as raw material, to prepare rice husk derived high efficient sorbents via chemical modification method. And the adsorption behavior have been investigated. The main contents are as follows:1. Rice husk-based bio-sorbent was successfully prepared by employing a two-step method, i.e., firstly carbonization of rice husk with sulfuric acid and followed by surface oxidation treatment with ammonium persulfate solution. The morphology and surface chemistry of rice husk-based adsorbent was characterized using SEM, FT-IR and XPS techniques.2. The influence of several factors including solution pH, contact time, temperature and ionic strength on the properties of Pb(II) were carried out to evaluate the adsorption performance. The kinetic and thermodynamic models were also investigated. The results revealed that the adsorption behavior of Pb(II) were in good agreement with the Langmuir isotherm and pseudo-second-order model. And the maximum adsorption capacity was 121.8 mg/g. Meanwhile, the regeneration of the rice husk-based bio-sorbent and the adsorption mechanism were also discussed.3. Solid RH (rice husk) residue (i.e., NaOH-treated RH) and FeCl3·6H2O were used as carbon and iron precursors, respectively, to prepare new magnetic adsorbents via a simple carbon-thermal method. The magnetic adsorbent was characterized using SEM, VSM, XRD and other techniques.4. The adsorption performance of Cr(VI) on rice husk derived magnetic sorbents were systematically discussed, and the kinetics and thermodynamic model of the adsorption process were studied. The result illustrated that in virtue of its porous structure, good magnetic properties, and high surface area, the resulting materials exhibited a large adsorption capacity and magnetic separation performance. The adsorption process obeyed the pseudo-second-order model and Langmuir isotherm. In addition, the adsorption mechanism was also investigated.