Investigation Of Preparation And Performance Of Activated Carbon From Polygonum Orientale Linn

A Low-cost and effective activated carbon was prepared from Polygonum orientale Linn by phosphoric acid activation. Its ability to remove the basic dyes, heavy metals and chlorophenol were evaluated. The effects of experimental parameters such as pH, ionic strength, initial concentration, contact time and temperature on the adsorption were investigated. The adsorption kinetics and thermodynamics were also discussed. Desorption studies were examined in further elucidating the mechanism of adsorption and the feasibility of regenerating the spent activated carbon.The pearation condition of PLAC was at a H3PO4 concentration of 45%, an impregnation ratio of 2.4:1, an impregnation time of 12h, an activated temperature of 450℃, an activated time of lh. The adsorbent appeared to have a coarse porous surface with irregular pores and is an amorphous structure. The surface area of PLAC was found to be 1398 m2/g, its average pore diameter was 4.4nm and it was mainly in mesoporous sturcture. There were many founctional groups on the surface such as: carboxylic, phenolic, lactonic and carbonylic, acidic groups were more than basic ones and carboxylic was the main group.Compared with other adsorpent, PLAC was a promising adsorbent for MG, RB, Pb (II) and 2,4-DCP removal as the adsorption capacity of PLAC were very high 480,556,98.39 and 220mg/g. The adsorption on PLAC was highly pH dependent and the removal efficiency of MG and Pb (II) were increased with increase in initial pH, while the removal percentage of RB and 2,4-DCP presented the opposite trend. Adsorption of basic dyes and 2,4-DCP on PLAC was weakly dependent on ionic strength, confirmed a chemical sorption mechanism. The adsorption of Pb(II) on PLAC was strongly dependent on pH and ionic strength, indicating an ion-exchange mechanism. The adsorption kinetics was found to be best represented by the pseudo-second-order kinetic model. The mechanism of the adsorption process was determined from the intraparticle diffusion model. The equilibrium adsorption data was well described by the Langmuir model. Thermodynamic study showed that the adsorption was a spontaneous process. It was an endothermic process for dyes and Pb(II), and exothermic process for 2,4-DCP.HCl could be selected as effective reagents for the regeneration of Pb(II) spent activated carbons, while ethanol and NaOH could be used as effective reagents for the regeneration of 2,4-DCP spent activated carbons. Therefore, PLAC has a great potential to be reused.