Chenglu Zhang

Adsorption of Pb(II) on activated carbon prepared from Polygonum orientale Linn.: kinetics, isotherms, pH, and ionic strength studies.

Low-cost activated carbon was prepared from Polygonum orientale Linn. (PL) by phosphoric acid activation. Its ability to adsorb Pb(II) ions from aqueous solutions was examined. Through SEM, XRD, BET, and FTIR analyses, the PL-activated carbon (PLAC) was found to have a porous structure with a surface area of about 1400 m(2)/g. Carboxyl groups played an important role in the adsorption of Pb(II) through blocking studies. The sorption system followed a pseudo second-order kinetic model, and the equilibrium time was obtained after 30 min. The adsorption isotherms were simulated well by the Langmuir model. The adsorption of Pb(II) on PLAC was strongly dependent on pH and ionic strength, indicating an ion-exchange mechanism. Regeneration studies showed that PLAC could be used several times by desorption with an HCl reagent.

Removal of cephalexin from aqueous solutions by original and Cu(II)/Fe(III) impregnated activated carbons developed from lotus stalks Kinetics and equilibrium studies

Lotus stalk activated carbon (AC) was produced by ultrasound digestion of lotus stalks in H(3)PO(4). Copper nitrate and iron nitrate were used to impregnate AC, producing Cu(II)-impregnated AC (AC-Cu) and Fe(III)-impregnated AC (AC-Fe). The modified ACs were characterized by N(2) adsorption-desorption isotherms, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The adsorption kinetics and isotherms of cephalexin (CEX) in aqueous solution were studied for AC, AC-Cu and AC-Fe. The kinetics and equilibrium data agreed well with the pseudo-second-order kinetics model and Freundlich isotherm model for all three adsorbents. The results also showed that the adsorption capacities of AC-Cu and AC-Fe were larger than the capacity of AC and AC-Fe was found to be the most effective at the removal of CEX in solution. Furthermore, batch experiments were conducted to study the effects of pH (2.5-10.5), initial concentration of CEX (4-16 mg/L), ionic strength (10-1000 mM) on CEX removal.

Textural properties and surface chemistry of lotus stalk-derived activated carbons prepared using different phosphorus oxyacids: adsorption of trimethoprim.

The preparation of activated carbons (AC-H(x)P(y)O(z)) by four kinds of oxyacids of phosphorus (H(3)PO(4), H(4)P(2)O(7), HPO(3) and H(3)PO(3)) activation of lotus stalk (LS) was studied, with a particular focus on the effect of these H(x)P(y)O(z) on both surface chemistry and porous texture. The XRD analysis of the samples after H(x)P(y)O(z) impregnation showed H(4)P(2)O(7) had the strongest influence on the crystallinity of LS. Thermo gravimetric studies of the pyrolysis of LS-H(x)P(y)O(z) indicated that these H(x)P(y)O(z) had a very different influence on the thermal degradation of LS. The prepared activated carbons were characterized by SEM, N(2) sorption/desorption isotherms, XRD, FTIR and Boehms titration. Batched sorption studies were performed to compare adsorptive properties of the carbons toward trimethoprim (TMP). The surface area and pore volume of AC-H(3)PO(4) and AC-H(4)P(2)O(7) were much higher than AC-HPO(3) and AC-H(3)PO(3). Boehms titration results indicated that AC-H(4)P(2)O(7) and AC-H(3)PO(3) possessed more acidic oxygen functionalities than AC-H(3)PO(4) and AC-HPO(3). The structure of the AC-HPO(3) was kept as its starting material after activation. Activation with H(3)PO(3) would result in the aromatization of the carbon. The sorption affinities of TMP follows an order of AC-H(4)P(2)O(7)>AC-H(3)PO(4)>AC-H(3)PO(3)>AC-HPO(3).

Preparation of activated carbon from cattail and its application for dyes removal

Activated carbon was prepared from cattail by H3PO4 activation. The effects influencing the surface area of the resulting activated carbon followed the sequence of activated temperature > activated time > impregnation ratio > impregnation time. The optimum condition was found at an impregnation ratio of 2.5, an impregnation time of 9 hr, an activated temperature of 500 degrees C, and an activated time of 80 min. The Brunauer-Emmett-Teller surface area and average pore size of the activated carbon were 1279 m2/g and 5.585 nm, respectively. A heterogeneous structure in terms of both size and shape was highly developed and widely distributed on the carbon surface. Some groups containing oxygen and phosphorus were formed, and the carboxyl group was the major oxygen-containing functional group. An isotherm equilibrium study was carried out to investigate the adsorption capacity of the activated carbon. The data fit the Langmuir isotherm equation, with maximum monolayer adsorption capacities of 192.30 mg/g for Neutral Red and 196.08 mg/g for Malachite Green. Dye-exhausted carbon could be regenerated effectively by thermal treatment. The results indicated that cattail-derived activated carbon was a promising adsorbent for the removal of cationic dyes from aqueous solutions.

Adsorption of Neutral Red onto Mn-impregnated activated carbons prepared from Typha orientalis.

Activated carbon was prepared from an inexpensive and renewable carbon source, Typha orientalis, by H(3)PO(4) activation and then impregnated with different Mn salts and tested for its Neutral Red (NR) adsorption capacities. The amount of Mn impregnated in the activated carbon was influenced by the anion species. Impregnation with Mn decreased the surface area, changed the pore size and crystal structure, and introduced more acidic functional groups such as carboxyl, lactone and phenol groups. The optimum adsorption performance for all the activated carbons was obtained at pH 3.7, Mn-Carbon dose of 0.100g/100ml solution and contact time 4.5h. The adsorption isotherms fit the Langmuir isotherm equation. The kinetic data followed the pseudo-second-order model. The thermodynamic parameters indicated that the processes were spontaneous and endothermic. According to these results, the prepared Mn modified activated carbons are promising adsorbents for the removal of Neutral Red from wastewater.

A note on the utilisation of spent mushroom composts in animal feeds

Abstract An Aspergillus species ( Aspergillus candidus 362) was isolated from contaminated spent Lentinus edodes compost. Using synchronous saccharification and fermentation (SSF) by the isolate and a yeast strain ( Endomycopsis fibuliger 253) under solid-state conditions, the crude protein contents were increased from 24.1 to 32.3% and from 28.4 to 36.7% for Pleurotus ostreatus - and Lentinus edodes -spent-compost media, respectively. The crude fibre contents of the composts were substantially decreased. After fermentation the in vitro digestibility of crude protein was improved to 70%. The total and essential amino acid contents made up 73.3 and 37.1% of the crude protein, respectively. The fermented spent composts media were highly-nutritious fodder for poultry and animals.

Adsorption of Basic Violet 14 in aqueous solutions using KMnO4-modified activated carbon.

In this paper, an activated carbon was prepared from Typha orientalis and then treated with KMnO(4) and used for the removal of Basic Violet 14 from aqueous solutions. KMnO(4) treatment influenced the physicochemical properties of the carbon and improved its adsorption capacity. Adsorption experiments were then conducted with KMnO(4)-modified activated carbon to study the effects of carbon dosage (250-1500 mg/L), pH (2-10), ion strength (0-0.5 mol/L), temperature, and contact time on the adsorption of Basic Violet 14 from aqueous solutions. The equilibrium data were analyzed by the Langmuir and Freundlich isotherms and fitted well with the Langmuir model. The pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to evaluate the kinetic data and the pseudo-second-order kinetics was the best with good correlation.

Sorption removal of cephalexin by HNO 3 and H 2 O 2 oxidized activated carbons

Cephalexin’s traces within pharmaceutical effluents have toxic impact toward ecological and human health. Low-cost activated carbon derived from Trapa natans husk was oxidized with hydrogen peroxide and nitric acid, and tested for their ability to remove cephalexin from aqueous solutions. Oxidization with H2O2 showed negative effect on the cephalexin sorption, whereas HNO3 oxidization improved the adsorption. The cephalexin adsorption isotherms on the native and HNO3 oxidized carbons correlated well with the Freundlich equation while their kinetics followed the pseudo-second order model. The removal of cephalexin by the native and HNO3 oxidized carbons was found to be most favored at low ionic strength and strong acidic conditions. Based on the thermal and FTIR analyses, the interaction mechanisms of the interaction between cephalexin and the carbons were proposed. Electrostatic attraction, hydrophobic interaction and chemical bonding with surface functional groups were demonstrated as primary mechanisms for cephalexin removal. The nitrogen functionalities on the carbon surface were considered to be an important factor affecting the adsorption process.

Development of carbon adsorbents with high surface acidic and basic group contents from phosphoric acid activation of xylitol

The present paper evaluated the feasibility of synthetizing activated carbons from xylitol with phosphoric acid activation at mild temperatures. Activation temperature (250–450 °C) and phosphoric acid to xylitol impregnation ratio (0.2–3 wt%) were varied during the synthesis of xylitol-based activated carbon, and the effects of these parameters on the textural and chemical properties of the final activated carbons were investigated by XRD, Raman, N2 adsorption and desorption, SEM, XPS and Boehms titration. The results of yield, XRD and Raman indicated that phosphoric acid activation enhanced the yields of activated carbons, and facilitated the formation of completely carbonized materials at low temperatures (around 250 °C) by comparing with charcoals derived from pyrolysis of xylitol. The porous structures of the activated carbons were developed after activation, and for each activation temperature, the carbons reached the maximum surface area at an impregnation ratio of 1.5. Due to the strong oxidizing radicals decomposed from phosphates, the produced carbons contain relatively high concentrations of acidic and basic surface groups. The total surface groups peaked at 6.08 mmol g−1 for activated carbon obtained at an activation temperature of 350 °C and impregnation ratio of 1.5. The Ni(II) adsorption capacity of the activated carbons was 4 to 7 folds that of the charcoals.

Preparation and characterization of charcoal from feathers and its application in trimethoprim adsorption

AbstractFeathers were utilized to prepare charcoal which could be used for the adsorption of the antibiotic trimethoprim (TMP). The physicochemical properties of the feather-derived charcoal were determined. The feather-derived charcoal had a surface area of 805.4 m2/g and a well-developed microporous structure. The contents of acidic and basic functional groups on feather-derived charcoal were 1.36 and 1.76 mmol/g, respectively, and pHpzc = 7.52. We studied the influences of adsorbent dose, initial TMP concentration, agitation time, temperature, pH, and ionic strength on the adsorption. The desorption properties of TMP-sorbed feather-derived charcoal were also tested. The adsorption kinetics accorded with the pseudo-second-order kinetic equation, and the overall rate of adsorption was mainly controlled by intra-particle diffusion. The adsorption isotherms for the TMP-feather-derived charcoal system are explained better by the Freundlich isotherm at lower temperature (293 K) while the Langmuir isotherm ga...