Structure Control Of Porous Carbon And Its Application In The Purification Of Drinking Water

With the developments of society and economy in China, population is persistently increased, water consumption also increase rapidly, and water pollution becomes a serious problem. At present, the mainly employed water purification methods in China are conventional treatments, which include coagulation, precipitation, filtration, and disinfection of liquid chlorine. Unfortunately, the effects of those purification methods are limited, and difficult to satisfy the increasingly stringent standards for drinking water. In addition, the secondary pollution to water caused by pipeline further reduce its quality.The quality of our drinking water is not so good, and it is imperative to invent new method for the purification of drinking water.It is well known that activated carbon (AC in brief) and activated carbon fibers (ACF in brief) belong to porous carbon. Due to their multiful pore structure and abundant surface functional groups,AC and ACF can be widely used in many fields including adsorption, and catalyst. Due to its good adsorption ability, porous carbon has good future in the deep purification of drinking water. In this paper, commercially available coconut shell based activated carbon and viscose-based activated carbon fiber were used as raw materials, and were impregnated by hydrogen peroxide and diammonium phosphate, respectively, then modified porous carbons were prepared by following carbonization and activation. Benzene, iodine and methylene blue were chosen as model compounds to determine the adsorption abilities of modified AC and ACF, and finally, the best parameters in the modified process were given. Nitrogen adsorption and infrared spectrum analysis were also used to analyze the porous carbon. The results showed that the adsorption abilities of AC and ACF were greatly affected by modified conditions.The best modified parameters for AC were as follows: carbonization and activation temperatures were 650oC and 870oC, carbonization and activation time were 30min and 60min, hydrogen peroxide concentration was 30%, and soaked time in hydrogen peroxide under 30oC was 4h. After modification, the value of benzene adsorption became 448.78mg/g from 134.54mg/g, the value of iodine adsorption turned to 840.92mg/g from 429.36mg/g. The best parameters in the modification process for ACF were as follows: the concentration of diammonium phosphate was 10%, immersed time was 60min, activation temperature was 850oC, and activation time was 30min. The adsorptions of benzene and methylene blue were 845.74mg/g, and 263.64mg/g, respectively. Nitrogen adsorption showed that the total pore volume of porous carbon, the surface area and the mesorpore rate increased significantly after modification. Infrared analysis showed that -OH and C=O were introduced in the final modified activated carbon, and phosphorus functional groups were introduced in the modified activated carbon fiber. Boehm titration showed that the surface acid group content of the modified AC and ACFs increased. Elemental analysis showed that the carbon content, hydrogen content and oxygen content of the modified AC decreased. For ACF modified by diammonium phosphate, the carbon content increased, while the hydrogen content and oxygen content decreased.In order to investigate the ability of porous carbon to remove organically polluted compound in water, AC and ACF after modification were used to remove phenol in water. The used amount of AC and ACF, the temperature, and the effect of pH value were studied. The results showed that phenol removal ratio was close to 100% for the modified activated carbon when the used amount of modified AC was 5g/L, the solution temperature was 35oC and the pH value was 6. The results also showed that phenol removal ratio was close to 100% for the modified activated carbon fiber when the used amount of modified ACF was 3g/L, the solution temperature was 15oC and the pH value was 6. The increase in phenol removal ratio of porous carbon after modification was mainly caused by pore structure and surface functional groups of porous carbon.