Study On The Adsorption Performance Of Dyes And Thiophenic Sulfide By Biomass-based Activated Carbon

With rapid development of economy and urbanization in our country, the pollution problems of dye wastewater and fuel combustion become increasingly serious trend. Due to high porosity, high surface area, and special surface properties of chemistry,"environmental guard"-activated carbon has been widely applied in gas and liquid adsorption fields. Using agriculture and forestry waste as raw material for the preparation of activated carbon is a hot point of research in the cleaning utilization technology of biomass energy. It has broad application prospect. This thesis mainly consists of the following aspects to investigate the preparation, liquid phase adsorption-separation of biomass-based activated carbon.1. Torreya testa residue was used as raw material to prepare the torreya testa residue based activated carbon by ZnCl2activation method. Porous structure, textural properities, surface oxygen functional groups of as-synthesized activated carbon was characterized by examinations with element analysis, N2adsorption isotherms, XRD, SEM and FTIR analyses, et al. Results shown the best conditions to prepare the activated carbon were pretreatment temperature120℃and time12h; carbonization temperature400℃and holding time2h; activation temperature500℃and time2h; temperature increase rate7℃·-min-1and the weight ratio of ZnCl2additives to the carbonized samples5:1. The torreya testa residue based activated carbon obtained under these conditions had the pore volumel.055mL·g-1, BET surface area974.85m2·g-1, pore size distribution1.60～3.10nm, and the adsorbed amount of iodine402.42mg·g-1, respectively.2. Finger citron residue was used as raw material to prepare the finger citron residue based activated carbon (FAC). It was tested as adsorbent for the removal of harmful dyes, namely, the anionic dye methyl orange (MO) and the cationic dye methylene blue (MB), from contaminated water. Adsorption capacity of FAC by various conditions were evaluated, including initial dye concentration, adsorbent dosage, contact time. solution pH, and temperature. As a result, the adsorption capacity of FAC is much higher than those of other types of activated carbons. The adsorption capacities of saturation were581.40and934.58mg/g for MB and MO, respectively. Three simplified kinetic models, namely, pseudo-first-order, pseudo-second-order, and intraparticle diffusion equations, were used to investigate the adsorption process. The pseudo-second-order equation was followed for the adsorption of MO and MB on FAC. The adsorption equilibrium data of two types of dyes onto FAC fitted well to the Langmuir isotherm models. Thermodynamic parameters showed adsorption of MO and MB was spontaneous and endothermic process. This work demonstrates that FAC could be employed as a low-cost alternative to commercially available activated carbons in the removal of dyes from wastewater.3. An oxidation method with peracetic acid was used to modify FAC. The modified FAC was characterized by N2adsorption, FT-IR, and base titration analyses. Moreover it has been used to evaluate the adsorption performance of thiophenic sulfide from fuel. The results show that after modification by concentrated peracetic acid for18h at25℃. the obtained materials show increase in pore volume from0.55to1.73mL/g, specific surface area from1,874to2,736m2/g, and the density of acidic surface oxygen complexes (C=O, C-OH, and COOH) from0.78to2.23mmol/g. IR and base titration results indicated that thiophene reacts with carbonyl groups to form phenols during desulfurization. Batch test results showed that the modified FACs show a good thiophene capture performance at30℃under the stirring speed of250rpm/min, the adsorbents/fuel ratio of1/20, and reaction time of30min. The equilibrium adsorption data were well represented by the Langmuir isotherm equation. The maximum sulfur adsorption capacity of oxidation treated sample (43.12mg/g) is superior to the most carbonaceous materials reported in the literature. The saturated adsorbents can be regenerated with stripping with alcohol solution and nearly100%of the desulfur capacity was recovered after regeneration.This thesis work demonstrates that torreya testa residue and finger citron residue could be employed as a waste material to prepare the activated carbon. Two kinds of biomass based activated carbon have a good application prospect in purification of dye wastewater and deep desulfurization field.