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Activated carbons were derived from Enteromorpha prolifera immersed in H 3 PO 4 solution or the H 3 PO 4 solution mixed with sodium benzenesulfonate (SBS), producing AC and AC-SBS. NaOH solution was employed in regeneration of ciprofloxacin (CIP)-loaded AC and AC-SBS to obtain RAC and RAC-SBS. The properties of the original and regenerated activated carbons were characterized by thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), N 2 adsorption/desorption isotherms and Fourier transform infrared spectroscopy (FTIR). Batched adsorption studies were carried out to compare CIP adsorption behaviors of the four carbons. The results suggested that the four samples exhibited higher proportions of mesopores and similar functional groups. Although AC displayed much higher specific surface area ( S BET ) (1045.79 m 2 /g) than AC-SBS (738.03 m 2 /g), its CIP adsorption capacity was much less than AC-SBS. The maximum adsorption capacity for AC, AC-SBS, RAC and RAC-SBS were found to be 250 mg/g, 286 mg/g, 233 mg/g and 256 mg/g, respectively, with the isotherms adhering to Langmuir isotherm model. The electrostatic attraction and cation exchange between CIP and the four carbons were the dominant adsorption mechanisms. Moreover, the thermodynamic parameters represented that the adsorption process had been confirmed to be a spontaneous and endothermic reaction. [ABSTRACT FROM AUTHOR]

The preparation of activated carbons (AC-(NH 4 ) x H y PO 4 ) from Iris tectorum (IT) with three kinds of ammonium phosphates ((NH 4 ) 2 HPO 4 , NH 4 H 2 PO 4 and (NH 4 ) 3 PO 4 ) activation was investigated, with a special attention paid to the effect of these (NH 4 ) x H y PO 4 on both physical and chemical properties. The prepared carbons were characterized by scanning electron microscope (SEM), N 2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR), and Boehm's titration. The surface area and total pore volume of AC-(NH 4 ) 3 PO 4 were much higher than AC-(NH 4 ) 2 HPO 4 and AC-NH 4 H 2 PO 4 , while AC-(NH 4 ) 2 HPO 4 had largest micropore volume ratio. Boehm's titration results suggested that AC-(NH 4 ) 2 HPO 4 possessed more acidic functional groups than AC-NH 4 H 2 PO 4 and AC-(NH 4 ) 3 PO 4 . Batch adsorption studies were carried out to compare adsorptive performances of the carbons toward Ni(II). The adsorption equilibrium data were in good agreement with Langmuir model. The maximum Ni(II) adsorption capacities of AC-(NH 4 ) 2 HPO 4 (40.00 mg/g) was higher than that of AC-NH 4 H 2 PO 4 (38.61 mg/g) and AC-(NH 4 ) 3 PO 4 (34.60 mg/g), resulting from the carbons higher content oxygen-containing functional groups which could adsorb more Ni(II) by cation exchange and electrostatic attraction. [ABSTRACT FROM AUTHOR]

Activated carbon was prepared from Enteromorpha prolifera (EP) by H3PO4 activation in the presence of doped cetyl trimethyl ammonium bromide (CTAB), producing EPAC–CTAB. The thermal decomposition process of the activated carbon substrate was identified by thermo-gravimetric analysis. Scanning electron microscope (SEM), N2 adsorption/desorption, Fourier transform infrared spectroscopy (FTIR), Boehm titration, and X-ray Photoelectron Spectroscopy (XPS) were employed to characterize the physicochemical properties of native EPAC and EPAC–CTAB. EPAC–CTAB exhibited smaller surface area (689.0m2/g) and lower total pore volume (0.361cm3/g) than those of EPAC (1045.8m2/g and 1.048cm3/g), while the number of acidic groups, oxygen and nitrogen groups on the surface of EPAC–CTAB increased through CTAB doping. The batch kinetics and isotherm adsorption studies of nickel(II) onto the adsorbents were examined and agreed well with the pseudo-second-order model and the Langmuir model. The maximum adsorption capacity determined from the Langmuir model was 16.9mg/g for EPAC and 49.8mg/g for EPAC–CTAB. Under acidic condition, the adsorption of nickel(II) onto EPAC and EPAC–CTAB was hindered due to ion competition and electrostatic repulsion. The results indicated that using CTAB as a dopant for EPAC modification could markedly enhance the nickel(II) removal. [Copyright &y& Elsevier]

Highlights: [•] ACFF was selected as the support material of NZVI. [•] Cr(VI) and total Cr removal on ACFF–NZVI was much higher than that on ACFF and NZVI. [•] Most toxic Cr(VI) was transformed to nontoxic Cr(III) by the reduction of ACFF–NZVI. [•] XPS and FTIR analysis were used to investigate the Cr(VI) removal mechanisms. [Copyright &y& Elsevier]

Abstract: Ferric nitrate was employed to modify activated carbon prepared from Iris tectorum during H3PO4 activation and ability of prepared activated carbon for removal of tetracycline (TC) was investigated. The properties of the activated carbon samples with or without ferric nitrate, ITAC-Fe and ITAC, were measured by scanning electron microscopy (SEM), N2 adsorption/desorption isotherms, Fourier transform infrared spectroscopy (FTIR) and Boehm's titration. The results showed that mixing with iron increased the BET surface area, total pore volume and the adsorption capacity as compared to the original carbon. FTIR and Boehm's titration suggested that ITAC-Fe was characteristic of more acidic functional groups than ITAC. Adsorption of TC on both samples exhibited a strong pH-dependent behavior and adsorption capacity reduced rapidly with the increasing solution pH. The adsorption kinetics agreed well with the pseudo-second-order model and the adsorption isotherms data were well described by Langmuir model with the maximum adsorption capacity of 625.022mg/g for ITAC and 769.231mg/g for ITAC-Fe. The present work suggested that ITAC-Fe could be used to remove tetracycline effectively from aqueous solutions. [Copyright &y& Elsevier]

In this research, activated carbon fiber heated by microwave (WACF) under nitrogen (N2) atmosphere adsorption of tetracycline antibiotics (TCs) was analyzed. WACF was obtained under the microwave radiation temperature of 600°C and the radiation time of 15 min. The properties of WACF were characterized by a scanning electron microscope (SEM), N2adsorption/desorption isotherms, and X-ray diffraction (XRD) compared with activated carbon fibers (ACF) without any treatment. WACF had lower surface area (1008 m2/g) but higher external surface area (429 m2/g) than ACF (surface area: 1153 m2/g; external surface area: 308 m2/g). Meanwhile, the adsorption efficiencies of TCs (including tetracycline hydrochloride (TC) and oxytetracycline hydrochloride (OTC)) on WACF were both increased by about 4 times. These results indicated that mesoporosity amplification of WACF played a crucial role in the adsorption capacity of the two TCs. The kinetics and equilibrium data were agreed well with the pseudo-second-order kinetics model (R2 > 0.99) and Langmuir isotherm model (R2 > 0.98), respectively. It suggested that the adsorption process was dominated by chemisorption. Batch experiments showed the maximum adsorption capacities for both adsorbates were 339 and 331 mg/g respectively at pH 2. [ABSTRACT FROM AUTHOR]

Abstract: Zizania latifolia was prepared for activated carbons with the method of H3PO4 activation. On the basis of Zizania latifolia activated carbons (ZLAC), adsorption of basic fuchsin (BF) on Fe(III) and Mn(II) modified ZLAC and ZLAC was investigated respectively. Surface morphology and function groups of ZLAC were measured by scanning electron microscopy (SEM), BET surface area and Fourier transform infrared spectroscopy (FTIR). Both of the results from the Fourier transform infrared spectroscopy and Boehm''s titration indicated that the ZLAC owned more acid oxygen functional groups than the alkaline functional groups. The discussions of contact time, dosage and pH were in favor for explaining the adsorption mechanism. The adsorption process agreed well with the pseudo-second-order kinetics (R2 >0.99) and the Langmuir isotherm equation (R2 >0.99), and the maximum adsorption capacity acquired can reach 238.10mg/g. The negative free energy (ΔG) and positive enthalpy (ΔH) indicated a spontaneous and endothermic adsorption process. Results also showed that the adsorption effect of Fe(III) and Mn(II) modified ZLAC was much better than ZLAC. [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]

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]

Highlights: [•] FeCl3, AlCl3 and MnCl2 were used as the assisted activator to produce carbons. [•] Doping with MnCl2 was favorable for the enlargement of activated carbon. [•] The assisted activator had good performance for holding more fixed carbon. [•] The maximum adsorption capacities followed the order of AC-Fe>AC-Al>AC-Mn>AC. [•] The XPS analysis was used to confirm the adsorption/transformation mechanism. [Copyright &y& Elsevier]

Highlights: [•] Leather waste was used as precursor. [•] H4P2O7 was used as the activation agent to make the structure of carbons. [•] Microwave technique was adopted to prepare activated carbon. [•] Maximum methylene blue capacity of 303.03mg/g was reported using Langmuir isotherm. [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]