The Preparation Of Non-pitch Binder Coal-based Activated Carbon And Application Research On Water Treatment

Coal-based activated carbon can effectively remove dissolved organicmatter (DOM) with its abundant pore structure and large surface area thatconventional water treatment processes can not be resolved. So, it is widelyused in micro-polluted water advanced treatment, and the development prospectis very wide.At present, in the process of industrial production of coal-based activatedcarbon, in addition to a large number of coal tar pitch as binder in the process,and environment is polluted serious. While the use of new organic non-pitchbinder process makes the activated carbon production difficulty due to the highcost. In view of the above problems, the research group independentlydeveloped a non-pitch binder, can achieve “low cost, high efficiency, moreclean” purpose. Then, cheap coal resources and the non-pitch binder as the mainraw material, the performance of activated carbon were systematically studiedthrough steam activation preparation process, oxidation-catalytic processes, micro-polluted water treatment and adsorption kinetics, the main research andachievments are as follows:1. The optimized operating conditions of the preparation of non-pitchbinder activated carbon is: carbonization temperature650℃, carbonization time45min, activation temperature880℃, activation time180min, water steam flow0.04mL·(min·g)-1, the obtained activated carbon has an iodine value853.8mg/g,carbon yield44.5%, specific surface area of684.3m2/g, total pore volume of0.3852cm3/g, micropore volume of0.2455cm3/g, the mesopore volume of0.1362cm3/g, belongs to the micro-pore and meso-pore advanced coal-basedactivated carbon.2. Carbon-oxygen microcrystalline heat-resisting macro-molecularcompounds structure C(O) were formed, and carbonyl (C=O), ether group(C-O-C) and nitryl (-NO2) were significantly increased after the coal wasoxidized by air and HNO3. The (002) diffraction peak intensity with increasingair temperature gradually weakened, and showing the changes of first decreasedand then increased with increasing the concentration of HNO3, and it wasweakest at air temperature of240℃and HNO3concentration of10%. Aftercross-linking and polymerization of carbonization, the degree of graphitizationgreatly reduced, carbon yield was71.0%after HNO3oxidation, compared with67.5%after air oxidation. When the pre-oxidation temperature of240℃, iodinevalue appeared maximum875.3mg/g, carbon yield55.4%and ash content41.3%; while the concentration of HNO3oxidation was10%, the iodine value appeared maximum970.7mg/g, carbon yield38.8%and ash content24.2%.3. After the oxidation, occurrence form C and O elements in coal-basedactivated carbon changed significantly. Where C elements mainly graphitecarbon and alkyl carbon (C-C)，the sum of two accounts for over70%of thetotal carbon content. After air oxidation, the relative content of graphite carbon,phenolic ether and carbonyl carbon increased largely, the relative content ofalkyl carbon and carboxyl carbon were reduced, the content of hydroxyl etheroxygen increased by21.7%and the content of carboxyl oxygen decreased by19.1%. After HNO3oxidation, the content of alkyl carbon and carboxyl carbonwas drastically reduced, phenolic ether carbon were increased, the content ofhydroxyl ether oxygen and carboxyl oxygen increased by37.0%and40.0%respectively, and the content of carbonyl oxygen decreased by36.3%.4. With the increase of nitrate content, iodine value appeared decrease afterthe first increase, and ash content appeared increasing trend after decreases first,the iodine value of activated carbon add KNO3obtained was higher than theother two nitrates, ash content was lower than the other two nitrates. When theKNO3content was15%, iodine value of maximum1184mg/g, and ash contentof minimum27.43%.5. The crystal products (K2O, Na2O2and Fe3C, etc.) and the gaseousproducts(O2and NO) of nitrate after carbonizion produce different degrees ofdamage on coal molecule, resulting in the degree of graphitization of carbidedecreased, the degree of preparation of the catalysis performance of activated carbon: KNO3>NaNO3>Fe(NO3)3. Including the catalytic mechanism is dividedinto two parts, one part of nitrate release O2and NO made intramolecularoxidation in the process of carbonization, the other part of the metal oxidegenerated played a catalytic role in the process of the activation reaction,generating large amounts of pore structure.6. NP-GAC mainly adsorbed alkanes, aromatic hydrocarbons andheterocyclic micro-molecular organics in the micro-polluted water by ByUV-VIS, which is in accordance well with heterogeneous Freundlich isothermaladsorption model: q=2.36488·C1.16011, and the lower limit of adsorption capacityis larger, and the adsorption capacity index is smaller. So, it is more suitable forthe organic matter of low concentration of water. The optimized conditions areas follows:50~60℃, pH7.80, dosage of activated carbon2.5g/L, andadsorption time150min. When the initial COD of micro-polluted water is9.66mg/L, the adsorption performance of NP-GAC is readily achieved under theoptimized conditions. The removal rate of COD and UV254can reached83.76%and97.78%, respectively.7. With the increase of adsorption time and temperature, adsorptionquantity of micro-molecular organics by activated carbon were increased, whereadsorption kinetics can be well in line with the pseudo-second-order dynamicsequation, and reaction rate formulae: K=499.49·exp(-25310/RT), whichActivation energy Ea=25.31kJ·mol-1, pre-exponential factor A=499.49g·(mg·min)-1, mainly physical adsorption.