Carbon surface chemical composition in para-nitrophenol adsorption determined under real oxic and anoxic conditions

Activated Carbon from Agricultural Wastes for Adsorption of Organic Pollutants

Agricultural waste materials (strawberry seeds and pistachio shells) were used for preparation of activated carbons by two various methods. Chemical activation using acetic acid and physical activation with gaseous agents (carbon dioxide and water vapor) were chosen as mild and environmentally friendly methods. The effect of type of raw material, temperature, and activation agent on the porous structure characteristics of the materials was discussed applying various methods of analysis. The best obtained activated carbons were characterized by high values of specific surface area (555-685 m²/g). The Guinier analysis of small-angle X-ray scattering (SAXS) curves showed that a time of activation affects pore size. The samples activated using carbon dioxide were characterized mostly by the spherical morphology of pores. Adsorbents were utilized for removal of the model organic pollutants from the single- and multicomponent systems. The adsorption capacities for the 4-chloro-2-methyphenoxyacetic acid (MCPA) removal were equal to 1.43-1.56 mmol/g; however, for adsorbent from strawberry seeds it was much lower. Slight effect of crystal violet presence on the MCPA adsorption and inversely was noticed as a result of adsorption in different types of pores. For similar herbicides strong competition in capacity and adsorption rate was observed. For analysis of kinetic data various equations were used.

The role of beaded activated carbon's surface oxygen groups on irreversible adsorption of organic vapors

The objective of this study is to determine the contribution of surface oxygen groups to irreversible adsorption (aka heel formation) during cyclic adsorption/regeneration of organic vapors commonly found in industrial systems, including vehicle-painting operations. For this purpose, three chemically modified activated carbon samples, including two oxygen-deficient (hydrogen-treated and heat-treated) and one oxygen-rich sample (nitric acid-treated) were prepared. The samples were tested for 5 adsorption/regeneration cycles using a mixture of nine organic compounds. For the different samples, mass balance cumulative heel was 14 and 20% higher for oxygen functionalized and hydrogen-treated samples, respectively, relative to heat-treated sample. Thermal analysis results showed heel formation due to physisorption for the oxygen-deficient samples, and weakened physisorption combined with chemisorption for the oxygen-rich sample. Chemisorption was attributed to consumption of surface oxygen groups by adsorbed species, resulting in formation of high boiling point oxidation byproducts or bonding between the adsorbates and the surface groups. Pore size distributions indicated that different pore sizes contributed to heel formation - narrow micropores (<7Å) in the oxygen-deficient samples and midsize micropores (7-12Å) in the oxygen-rich sample. The results from this study help explain the heel formation mechanism and how it relates to chemically tailored adsorbent materials.

Surface-modified activated carbon with β-cyclodextrin--Part II. Adsorption properties

Sorption properties of surface modified activated carbon (AC) with p-nitrophenol (PNP) and methylene blue (MB) in aqueous solution were investigated. The calculated surface areas for AC and surface modified AC were compared using nitrogen sorption and a dye-based method. The surface areas of AC and the surface modified AC with glutaraldehyde (AC-β-CD) (1:10:10⁹) and 1,4-phenylene diisocyanate (ACPDICD) measured by nitrogen sorption were 1,269 m²/g, 103 m²/g, and 95 m²/g, respectively (Langmuir model) and 956 m²/g, 74 m²/g, and 69 m²/g (BET model), respectively. However, the calculated surface areas for the dye-based method (PNP; pH 6.00) for AC, AC-β-CD(1:10:10⁹), and ACPDICD was 1,035 m²/g, 814 m²/g, and 76 m²/g (Langmuir model), respectively and 1,491 m²/g, 1,669 m²/g, and 92 m²/g (BET model), respectively. The corresponding surface areas for the dye-based method (MB; pH 8.40) for AC-β-CD(1:10:10⁹) and ACPDICD was 263 m²/g and 171 m²/g (Langmuir model), respectively and 1019 m²/g and 182 m²/g (BET model), respectively. The sorption capacity (Q(m)) and binding affinity characteristics [K(F)(L/g), K(L)(g/mol), and K(BET)(L/g)] were estimated at room temperature at equilibrium conditions using several sorption isotherm models.

Reduction of nitro phenols using nitroreductase from E. coli in the presence of NADH

The reductions of nitrophenols catalyzed by nitroreductase from E. coli in the presence of NADH were investigated in this paper. 4-Aminophenol and 4-hydroxylaminophenol were found in the reductive products of 4-nitrophenol and the maximum reductive ratio was about 83.49% when the reaction time was 70 min; 4,6-dinitro-2-pimelie kelone was found in the reductive products of 2,4-dinitrophenol and the maximum reductive ratio was about 75.28% when the reaction time was 80 min; 2,4-dinitrophenol and 4,6-dinitro-2-pimelie kelone were found in the reductive products of 2,4,6-trinitrophenol and the maximum reductive ratio was about 62.08% when the reaction time was 100 min. The similar reductive ratios of nitrophenols were obtained under aerobic and anaerobic conditions. The results indicated that nitroreductase was an oxygen-insensitive enzyme.