Activated Carbons Derived From Rice Husk For Sorption Of Semi-volatile Phenol In The Liquid And Gas Phase

With the rapid development of society,the pollutions of atmospheric environment and aquatic environment caused by industrial waste gas and water cannot be ignored.Especially in response to the challenges posed by volatile organic pollutants（VOCs）,a variety of VOCs can lead to significant harm to environment and human health.Amongst,phenol as one of the toxic semi-VOC widely exists with large quantities in industrial wastewaters and in tar,which is extremely corrosive and combustible.In recent years,researches on VOCs sorption by activated carbons has been increasingly carried out and achieved good results.In this study,the influencing factors of the synthesis of activated carbon from the abundantly rice husk（RH）were investigated with the aim of obtaining high-performance porous carbons.Additionally,the synthesized porous biocarbons were comparatively evaluated to adsorb phenol compounds in different phases（e.g.,liquid,gas）.The key research outputs are given as follows:（1）The synthesis of activated carbon using one-step and two-step methods were comparatively studied.With the optimal conditions（i.e.,the pyrolysis temperature:450 ^oC,the ratio of alkali KOH to carbon:3 and the activation temperature:750 ^oC）,the biocarbon prepared by the two-step pyrolysis showed the highest specific surface area(S_BET:2138 m²/g).Compared with the one-step pyrolysis,the two-step pyrolysis can produce a relatively high yield of bio-carbon.At the same activation temperature,the mass ratio of KOH had a significant effect on the specific surface area and porosity of activated carbon.（2）Activated biocarbon can effectively adsorb phenol in the liquid phase,and the adsorption process can be completed in only a few minutes.In particular,the maximum adsorption capacity of AB2-3-750 can reach about 201 mg/g,which is mainly attributed to its abundant surface pore and high specific surface area;the adsorption isotherm of phenol on activated bio-char can be fitted by Langmuir model,indicating that the adsorption behavior is monolayer;the adsorption process can be fitted by pseudo-second-order model,indicating that phenol adsorbs on activated bio-char.It is most likely controlled by chemical adsorption.（3）Activated biocarbon can also effectively adsorb phenol in the gas phase.By comparing the properties of activated carbon prepared from raw rice husk（RH）and pelletized rice husk（RHP）,it was found that RHP chars were beneficial to the development of micro-mesoporous carbon with hierarchical structure,thus enhancing the migration of phenol molecules from outer layer to inner adsorption sites.In addition,the RHP-derived activated carbons showed a higher performance on the phenol adsorption,with a maximum adsorption capacity of 735 mg/g.So far,few work has reported on the sorption of gaseous phenol by activated carbons.Hence the present work comparatively studied the adsorption of phenol in the liquid and gas phases by RH-derived biocarbons.Finally,a feasible strategy was built for the synthesis of sustainable activated carbons from RH that can be used for removal of semi-volatile phenol in the industrial plants.