Degradation of phenol using a combination of granular activated carbon adsorption and bipolar pulse dielectric barrier discharge plasma regeneration

A combined method of granular activated carbon（GAC） adsorption and bipolar pulse dielectric barrier discharge（DBD） plasma regeneration was employed to degrade phenol in water.After being saturated with phenol,the GAC was filled into the DBD reactor driven by bipolar pulse power for regeneration under various operating parameters.The results showed that different peak voltages,air flow rates,and GAC content can affect phenol decomposition and its major degradation intermediates,such as catechol,hydroquinone,and benzoquinone.The higher voltage and air support were conducive to the removal of phenol,and the proper water moisture of the GAC was 20%.The amount of H2 O2 on the GAC was quantitatively determined,and its laws of production were similar to phenol elimination.Under the optimized conditions,the elimination of phenol on the GAC was confirmed by Fourier transform infrared spectroscopy,and the total removal of organic carbons achieved 50.4%.Also,a possible degradation mechanism was proposed based on the HPLC analysis.Meanwhile,the regeneration efficiency of the GAC was improved with the discharge treatment time,which attained 88.5% after 100 min of DBD processing.

Batch Studies for the Removal of a Hazardous Azo Dye Methyl Orange from Water through Adsorption on Regenerated Activated Carbons

The study of the performances of regenerated activated carbons for the adsorption of MO(methyl orange)in an aqueous medium was carried out with the aim to evaluate the adsorption capacities of these activated carbons.Three regenerated activated carbons issued from the unit of oil treatment of the thermal power station of Dibamba(Cameroon)-DPDC(Dibamba Power Development Company)were obtained thermally and chemically.These three samples(namely CAR 400℃(chemical regenerated activated carbon at 400℃),CAR 700℃(physical regenerated activated carbon at 700℃)and CAR 900℃(physical regenerated activated carbon at 900℃))and the non-used one CA were characterized by iodine number,XRD(X-ray Diffraction)and FTIR(Fourier-transform infrared spectroscopy).MO adsorption tests were performed in batch mode;this technique allowed the study of the influence of the parameters such as:the contact time,the initial’s MO concentration and the pH.Moreover,different kinetic models(first-order,pseudo-second-order and Webber and Morris intra-particle diffusion)and adsorption isotherms(Langmuir and Freundlich)are used for the evaluation of adsorption capacities.The physicochemical characterization of these adsorbents showed that they were micro-porous(iodine value:600 mg/g)and strongly crystallized according to their regeneration pathways.The influence of the parameters revealed that the adsorption of MO is the most favorable for concentrations from 5 to 25 mg/L(for materials CA and CAR 400℃)and 10 to 25 g/L(for materials CAR 700℃ and 900℃);and that it was maximum in acid medium(at pH=3 on the materials CA,CAR 400℃,CAR 900℃ and at pH=5 on the material CAR 900℃).The modeling of the adsorption kinetics of MO has revealed the conformity of the kinetic model of pseudosecond-order and intra-particle diffusion for some of these materials.The study of isotherms has shown that the Langmuir isotherm best describes the adsorption of MO on most of these adsorbents.

Thermal defluorination behaviors of PFOS,PFOA and PFBS during regeneration of activated carbon by molten salt

Current study proposes a green regeneration method of activated carbon(AC)laden with Perfluorochemicals(PFCs)from the perspective of environmental safety and resource regeneration.The defluorination efficiencies of AC adsorbed perfluorooctanesulfonate(PFOS),perfluorooctanoic acid(PFOA)and perfluorobutanesulfonate(PFBS)using three molten sodium salts and one molten alkali were compared.Results showed that defluorination efficiencies of molten NaOH for the three PFCs were higher than the other three molten sodium salts at lower temperature.At 700°C,the defluorination efficiencies of PFOS and PFBS using molten NaOH reached to 84.2%and 79.2%,respectively,while the defluorination efficiency of PFOA was 35.3%.In addition,the temperature of molten salt,the holding time and the ratio of salt to carbon were directly proportional to the defluorination efficiency.The low defluorination efficiency of PFOA was due to the low thermal stability of PFOA,which made it difficult to be captured by molten salt.The weight loss range of PFOA was 75°C–125°C,which was much lower than PFOS and PFBS(400°C–500°C).From the perspective of gas production,fluorine-containing gases produced from molten NaOH-treated AC were significantly reduced,which means that environmental risks were significantly reduced.After molten NaOH treatment,the regenerated AC had higher adsorption capacity than that of pre-treated AC.