Chemical Modification Of The Mesoporous Activated Carbon Adsorption Properties Of Pb (2 +)

Mesoporous activated carbon (MeAC) has good adsorption properties for heavy metalions, and its abundant mesopore provide channel for liquid propagate. In order to improvethe adsorption properties, MeAC was modified by oxidation, sulfonation and alkalization.Adsorption properties of Pb²⁺ ion with raw and modified MeAC was examined using staticadsorption method. The regeneration of modified MeAC was also studied.The modified MeAC samples were characterized by Boehm titration, adsorption anddesorption of nitrogen at 77K, pore size distribution, fourier transform infraredspectroscopy (FT-IR), laman spectroscopy, TG-DTA and XRD. The results of Boehmtitration showed that the acidic group amount of oxidated MeAC (MeAC-O) andsulfonated MeAC (MeAC-O-huang) increased 500% and 600% respectively, comparedwith raw MeAC. As modification extent of oxidation, sulfonation and alkalizationincreased, all of the specific surface area, mesopore content, and average pore diameterwere decreased.The raw MeAC's and modified MeAC's static adsorption of Pb²⁺ in aqueous solutionhad been studied. The results indicated that all the modified MeAC had better adsorptioncapacity of Pb²⁺ than MeAC.When C₀ was less than 140mg·L^-1, the equilibrium time ofadsorption of MeAC-O-Na and MeAC-O-huang-Na was only 5min. Their equilibriumadsorption capacity was 148.6mg/g and 218.8mg/g respectively, and enhanced 500% and800% respectively, compared with that of MeAC. Furthermore, they keep high adsorptionproperties in a wide range of pH values (3-5.7) in the solution of 70 mg·L^-1, and the Pb²⁺removal efficiency was nearly 100%.The adsorption mechanism of MeAC for Pb²⁺ is main upon ion exchange, and partlyphysical adsorption of MeAC's surface. When the MeAC adsorbed Pb²⁺, chemicaladsorption was dominant. The influence of the acidic group was greater than specificsurface area on adsorption capacity.The acid-alkali regeneration method was much better than the dilute nitric acidregeneration method.And higher concentration of nitric acid made regeneration easier.MeAC-O-Na and MeAC-O-huang-Na adsorbents satured with Pb²⁺ were regenerated andthen were used to static adsorption repeatedly. The results indicated adsorption efficiencyreached above 80% and 90% respectively after three cycles.