A Facile Process For The Preparation Of High-quality SiO₂ From Rice Husk Ash

As the world's largest rice-producing country,China can produce hundreds of millions of tons of rice annually.Rice husk,a by-product of rice processing,with an output of about100 million tons a year.Due to its huge quatity and difficult to transport,it is usually directly burnt or piled on site,these treatments causes not only great environmental pollution but also huge resource waste.and these do not meet the sustainable development requirements.Rice husk,as a cheap,renewable clean energy resource,its comprehensive utilization has become an key problem of social economical and ecological improtance.A facile and effcient process for the preparation of high-quality SiO₂ from Rice Husk Ash was first reported with rice husk ash,Na₂CO₃ and 2-Acrylamido-2-methylpropane sulfonic acid as raw materials,In the process,rice husk ash and Na₂CO₃ was first reacted to form sodium silacate,andthen it reacts with 2-Acrylamido-2-methylpropane sulfonic acid?AMPS?as precipitant and dispersant to give SiO₂ nanoparticle.Morphology?microstructure and properties of the synthesized particles were characterized by ICP,X-ray diffraction?XRD?,FT-IR analysis,SEM analysis.The suitable reaction condition is obtained as follows:at 40?,mass ratio of 25%AMPS solution to 0.2mol/L Na₂SiO₃ was2:1,after the addition,the system rests for 3h.In these conditions,yield of SiO₂ is 99.0%,with nearly spherical particle of the average grain diameter 100nm,specific surface area of425m²/g and pore diameter of 4nm,It can be used as a high-class reinforcing agent for tires and other polymer composites.In the experiment,precipitation agent AMPS can be reused10 times after acidification,and the yield of nano-silicon dioxide particles was still up to98%.The carbon,the left substance after the extraction of SiO₂ from the ash was treated with NaOH to obtain activated carbon material.the optimal reaction parameters is as follows:calcination temperature 600?,mass ratio of NaOH to carbon was 3:1,reaction time 3h,at these conditions,an activated carbon with specific surface area of 968m²/g and pore diameter of 5nm was obtained,its quality is better than that of the product standard requirements,and can be used as an efficient adsorpant.These results above provides a new way to the efficient utilization of rice husk ash with great industrial development potential.