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Abstract: A composite sorbent (ACprepared by grafting amine-group onto activated carbon (AC). Both raw AC and ACcharacterized by scanning electron microscopy (SEM), Fourier transformed infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). Batch experiments with variable pH, time, and concentrations of Cr(VI) were conducted to evaluate the sorption performance of Cr(VI) by both adsorbents from aqueous solutions. The total chromium in the aqueous solution was also recorded to study the mechanism of adsorption/transformation of Cr(VI). The ratio of the amount of Cr(VI) to Cr(III) on the sorbent was confirmed by the XPS analysis results. Langmuir, Freundlich and Temkin adsorption isotherms were used to fit the experimental equilibrium data and values of the parameters of the isotherms were reported. When compared with the untreated activated carbon, the modified activated carbon provided more faster kinetics and the sorbent exhibits greater adsorption capacity for chromium(VI) by comparing the maximum adsorption capacity calculated by Langmuir model. Overall, ACffectively remove Cr(VI) from aqueous solutions under a wide range of experimental conditions. [Copyright &y& Elsevier]

Abstract: The pore structure, chemical properties and adsorption behavior of activated carbons (ACs) derived from Arundo donax Linn using H4P2O7 activation by conventional (AAC) and microwave heating methods (MAAC) were compared. AAC was produced by carbonizing/activating at 600°C for 1h in a muffle furnace. MAAC was prepared with radiation power of 700W and radiation time of 15min. N2 adsorption/desorption isotherms, Boehm titration, Fourier-transform infrared spectroscopy (FTIR) and adsorption capacity of ciprofloxacin (CIP) were used for this purpose. MAAC exhibited larger surface area (1567m2/g) and larger micropore surface area (631m2/g). Results from Boehm’s titration and Fourier-transform infrared spectra suggested that AAC was characteristic of more acidic functionalities than MAAC. It was shown that AAC presented better performance for CIP adsorption per unit surface area. The influence of the textural and surface properties of the adsorbents on the CIP adsorption was discussed. [Copyright &y& Elsevier]

Abstract: The objective of this research is to produce high surface area–activated carbon derived from cotton linter fibers by fused NaOH activation and to examine the feasibility of removing oxytetracycline (OTC) from aqueous solution. The cotton linter fibers activated carbon (CLAC) was characterized by N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The results showed that CLAC had a predominantly microporous structure with a large surface area of 2143m2/g. The adsorption system followed pseudo-second-order kinetic model, and equilibrium was achieved within 24h. The equilibrium data were described well by Langmuir isotherm. Thermodynamic study showed that the adsorption was exothermic reaction at low concentration and became endothermic nature with the concentration increasing. Competitive adsorption took place in the weakly acidic to neutral conditions. Under the strong acidity or strong alkaline condition, the adsorption of the oxytetracycline was hindered by electrostatic repulsion. The adsorption mechanism depended on the pH of the solutions as well as the pK a of the oxytetracycline. [Copyright &y& Elsevier]

Abstract: Two activated carbons employing Cyperus alternifolius as precursor were produced by using two different activating agents, H3PO4 and H4P2O7 (AC-H3PO4 and AC-H4P2O7). Both of activated carbons were allowed by single-step to get carbonized at 450°C in a muffle furnace for 1h. Activated carbons differed with the physical structure and chemical properties which were derived from Scanning Electron Microscope, N2 adsorption/desorption isotherms and Fourier-transform infrared spectroscopy (FTIR). Batched sorption studies were performed to compare the ciprofloxacin (CIP) adsorption properties of two carbons. The results indicated that AC-H3PO4 had 1066.4m2/g of surface area and 1.151cm3/g of total pore volume, while AC-H4P2O7 had 1040.3m2/g of surface area and 1.227cm3/g of total pore volume. Moreover, AC-H4P2O7 exhibited a higher portion of mesopores than AC-H3PO4. Fourier transform infrared spectra indicated two samples had similar functional groups. For both adsorbents, the adsorption kinetics followed the pseudo-second-order model. The adsorption equilibrium data were very well represented by three commonly used isotherm model for AC-H3PO4 (Langmuir, Freundlich and Temkin equations). As for AC-H4P2O7, the adsorption isotherm models fitted the data in the order: Langmuir>Temkin>Freundlich isotherms. The thermodynamic parameters indicated that the adsorption of CIP onto both adsorbents was spontaneous and thermodynamically favorable, with exothermic nature of the adsorption of CIP onto AC-H3PO4 and endothermic nature onto AC-H4P2O7. [Copyright &y& Elsevier]

Abstract: The paper presents advantages and limitations of microwave heating in preparation of lotus stalk-based activated carbon by comparing the characteristic and adsorption properties of carbons with microwave (Mic-LSAC) and conventional (LSAC) heating methods employing H3PO4 as chemical agent. Mic-LSAC was produced with radiation power of 700W and radiation time of 15min. LSAC was allowed by single step to get carbonized at 450°C in a muffle furnace for 1h. Both produced carbons showed typical Type IV nitrogen adsorption isotherms. Mic-LSAC had large surface area of 1434m2/g and micropore volume of 1.337cm3/g, while LSAC had surface area of 1220m2/g and micropore volume of 1.191cm3/g. Moreover, Mic-LSAC had higher portion of mesopores than LSAC. Boehm''s titration results and Fourier transform infrared spectra indicated that Mic-LSAC possessed smaller acidic oxygen functionalities. Mic-LSAC had higher pHpzc, more ordered stacking of layer compared to LSAC. For both adsorbents, the adsorption kinetics followed the pseudo-second-order model and the adsorption equilibrium data were very well represented by the Langmuir isotherm. The maximum adsorption capacities obtained at pH 2.80 were 564.97mg/g and 537.63mg/g for Mic-LSAC and LSAC, respectively. The differences of textual and chemical characteristics caused by heating method were related to adsorption capacity. [Copyright &y& Elsevier]

Perfluorooctanoic acid (PFOA) is an emerging pollutant that is non-biodegradable and presents severe environmental and human health risks. In this study, we present an effective and mild approach for PFOA degradation that involves the use of nitrogen-doped carbon foam anchored with nanoscale zero-valent iron (nZVI@NCF) to activate low concentration peroxymonosulfate (PMS) for the treatment. The nZVI@NCF/PMS system efficiently removed 84.4% of PFOA (2.4 μM). The active sites of nZVI@NCF including Fe0 (110) and graphitic nitrogen played crucial roles in the degradation. Electrochemical analyses and density functional theory calculations revealed that nZVI@NCF acted as an electronic donor, transferring electrons to both PMS and PFOA during the reaction. By further analyzing the electron paramagnetic resonance and byproducts, it was determined that electron transfer and singlet oxygen were responsible for PFOA degradation. Three degradation pathways involving decarboxylation and surface reduction of PFOA in the nZVI@NCF/PMS system were determined. Finding from this study indicate that nZVI@NCF/PMS systems are effective in degrading PFOA and thus present a promising persulfate-advanced oxidation process technology for PFAS treatment. [Display omitted] • NZVI@NCF/PMS efficiently degraded PFOA in 120 min. • Fe0 (110) and graphitic N of nZVI@NCF favored PFOA degradation. • Electron transfer and singlet oxygen played important roles in PFOA degradation. • Three PFOA degradation pathways involving decarboxylation and surface reduction are presented. [ABSTRACT FROM AUTHOR]

Arundo donax Linn -based resin (ADI-resin) and Arundo donax Linn -based activated carbon (ADI-AC) were prepared for phosphate elimination from stream. Characteristics (BET surface area, Zeta potential, SEM, FTIR, and Raman spectra) of the biosorbents indicated that some required functional groups have been grafted onto the ADI-resin. The regenerated ADI-resin achieved 92–94% of adsorption capacity even after seven cycles of adsorption and desorption. However, only about 15–25% of phosphate could be desorbed from the ADI-AC at the same desorption conditions. A stratification-packed column with different particles sizes of ADI-resin/ADI-AC was also designed. When the stratified resins with different particle sizes were introduced, the bed utilization of ADI-resin was greatly enhanced. In contrast, the stratified ADI-AC packed in column was not effective as the performance of stratified ADI-resin. [ABSTRACT FROM AUTHOR]

Highlights: [•] Enteromorpha prolifera-based activated carbon was activated by KOH and H4P2O7. [•] The properties of carbons prepared by H4P2O7 and KOH were compared. [•] The activated carbon with high surface area of 3500m2/g was prepared by KOH. [•] The prepared carbons exhibited significant adsorption capacity for GR. [ABSTRACT FROM AUTHOR]

Highlights: [•] The lignin-based activated carbon was prepared by physical activation with steam. [•] The influences of various process parameters were investigated. [•] The optimum preparation conditions were determined. [•] The lignin-based carbon prepared by steam activation exhibited a mesoporous structure. [•] The static adsorption experiment and adsorption isotherms were studied. [Copyright &y& Elsevier]

Abstract: In this study, utilization of leather waste (LW) as precursor for activated carbon preparation by physical (steam) and chemical (pyrophosphoric acid, H4P2O7) activation in different conditions (carbonization temperature, carbonization time and impregnation ratio) is discussed. Thermal gravimetric analysis of LW-H4P2O7 indicated that H4P2O7 as the activator promotes the formation of carbonaceous material. The activated carbons obtained under the best conditions were characterized using N2 adsorption/desorption isotherms, X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The preparation principle of activated carbon with different methods was also studied. Batch adsorption studies were performed to evaluate the adsorption properties toward methylene blue (MB). Activated carbon produced by H4P2O7 activation showed higher yield, lower S BET, more functional groups and higher adsorption capacities for MB than the carbons prepared by steam activation. Adsorption experiment indicated that the adsorption data fitted the Langmuir equation better than Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherms, and the capacity of adsorption for AC-H4P2O7 was superior to AC-steam, indicating the mechanisms of π–π electron-donor–acceptor (EDA) interaction, cation exchange and hydrogen bond were involved due to the more functional groups. The adsorption has been confirmed to be a spontaneous and endothermic process. [Copyright &y& Elsevier]

Abstract: Low-cost activated carbon with high surface area was prepared from lignin of papermaking black liquor (BL) by KOH activation with pre-carbonization method. The effects of lignin/KOH ratio, activation temperature and activation time on the BET surface area were investigated. In addition, the adsorption capacity of Ni(II) on BLAC was also studied. Through BET surface area, scanning electron microscopy, Fourier transformed infrared spectroscopy and thermo gravimetric analysis, the BL-activated carbon (BLAC) was discovered to have porous structure with a high surface area up to 2943m2/g. The results showed that the lignin/KOH ratio was the main factor influencing the surface area and the maximum surface area activated carbon was obtained at lignin/KOH ratio of 3:1, the activation temperature of 750°C and the activation time of 1h. The sorption experiments indicated that the pseudo-second-order model was well fitted the kinetic data and the adsorption equilibrium data were better simulated by Langmuir model. The adsorption ability of Ni(II) increased with increasing pH, indicating the electrostatic attraction mechanism. [Copyright &y& Elsevier]