Runping Han

Malachite green adsorption onto natural zeolite and reuse by microwave irradiation

Natural zeolite was used for the removal of malachite green (MG) from aqueous solution in batch mode and reused by microwave irradiation. The isotherm data were analyzed by the Langmuir, Freundlich, Redlich-Peterson, and Koble-Corrigan isotherm model. The better fit for the equilibrium process was Koble-Corrigan model. The kinetic studies indicated that the adsorption followed the pseudo-second-order kinetic. Thermodynamic calculations showed that the adsorption was spontaneous and endothermic process. Spent zeolite was treated by microwave irradiation and it was found that yield of regeneration was 85.8% in the case of microwave irradiated time 10 min at 160 W.

Characterization of bio-char from pyrolysis of wheat straw and its evaluation on methylene blue adsorption

Abstract Bio-char, a by-product from the slow pyrolysis of wheat straw, was characterized and investigated as an adsorbent for the removal of cationic dye, methylene blue (MB) from solution. Elemental analysis, Fourier transform infrared spectrum, X-ray diffraction, and pH of point of zero charge (pHpzc) were presented. Adsorption studies were performed at different pH, salt concentration, contact time and dye concentration in the batch mode. The results showed that there were—OH and other functional groups on the surface of bio-char and the pHpzc of the bio-char was 7.8. The value of solution pH 8–9 was best for the MB adsorption quantity. Salt that coexisted in solution was not favored in MB adsorption. The equilibrium data were modeled with Langmuir, Freundlich, and Sips equations. Overall, the data were best fitted with the Sips model. The maximal adsorption capacity from the Sips model was 12.03 ± 0.41 mg/g at 293 K. Thermodynamic parameters were calculated and the results show that the process was s...

Cr(VI) removal via anion exchange on a silver-triazolate MOF.

Gram-scale synthesis of a silver-triazolato framework - {[Ag8(tz)6](NO3)2·6H2O}n (1-NO3; tz-=3,5-diphenyl-1,2,4-triazolate) - has been achieved, enabling the systematic investigation of its anion-exchange properties. Our experimental results show that the anion-exchange pattern of 1-NO3 conforms to the so-called Hofmeister bias, which has been correlated to the hydrophobic nature of the MOF pores, and can be understood by considering the difference between the hydration energies of the exchanging anions. Furthermore, 1-NO3 displays a fast, efficient, and reversible adsorption of HCrO4- (via anion-exchange) from Cr(VI)-containing aqueous solution (Qmax=37.0 Cr mg/g, 303K), rendering it a promising prototype of a recyclable MOF for Cr(VI) removal.

Study of congo red adsorption onto chitosan coated magnetic iron oxide in batch mode

Abstract The adsorption behavior of congo red (CR) on a magnetic composite (chitosan coated magnetic Fe3O4 particle) was studied as a function of initial solution pH, salt concentration, contact time, initial concentration of CR in batch mode. Change of solution pH, adsorption isotherms and their thermodynamic parameters (ΔG0, ΔH0, ΔS0) were discussed. There was little effect of initial pH and salt concentration. The experimental data were fitted to Langmuir, Freundlich, Temkin, Koble–Corrigan and Toth isotherm models. It was found that the Langmuir, Koble–Corrigan and Toth models provided good correlation. The adsorption capacity of CR was obtained from the Langmuir model and found to be 42.62, 55.68, 56.66 mg/g−1 at 295, 305, 315 K, respectively. The thermodynamic parameters indicated spontaneous and endothermic process. It was concluded that the adsorption process was main chemical adsorption and the dye-loaded adsorbent can be reused by regeneration with dilute NaOH solution.

Biosorption of methyl orange from aqueous solutions using cationic surfactant-modified wheat straw in batch mode

AbstractIn this paper, the characterization of wheat straw (WS) and cetyl trimethyl ammonium bromide (CTAB) modified wheat straw (MWS) was determined by Fourier transform infrared spectroscopy (FTIR) and X-ray fluorescence (XRF), indicating that CTAB had entered into the structure of WS successfully. Then, MWS was used as adsorbent for the removal of methyl orange dye (MO, anionic dye) from aqueous solution in batch mode. The experiments were carried out by exploring the most suitable conditions including solution pH, MWS dosage, dye initial concentration, temperature, and contact time. Biosorption capacity of MWS for MO is 50.4 mg g−1 at 303 K under the optimum condition of pH of 3, MWS dosage of 1.00 g L−1, contact time of 520 min. The Freundlich and Temkin models were all successful in depicting the equilibrium. The kinetic process can be predicted well by the Elovich, pseudo-second-order and intraparticle diffusion model. In addition, the thermodynamics parameters indicated the biosorption process was...

Biosorption of copper ion by natural and modified wheat straw in fixed-bed column

Adsorption of copper ions from aqueous solution was studied by natural wheat straw (NWS) and modified wheat straw (MWS) with citric acid in fixed-bed column. The experiments were conducted to investigate the effects of the bed depth, the flow rate, and the influent concentration of copper ions. The column data were fitted by the Thomas model using nonlinear regressive analysis while bed depth/service time analysis (BDST) model was applied at different bed depth. The Thomas model was found suitable for the description of breakthrough curve. The bed depth service time (BDST) model was applied to predict the service times with other flow rate and initial concentration. The theoretical breakthrough curve was compared with experimental breakthrough curve profile in the dynamic process. The copper-loaded adsorbent was regenerated using hydrogen chloride solution. The results showed that the adsorption capacity of MWS for copper ion was higher than NWS and both NWS and MWS can be reused.

Biosorption of methylene blue by natural and chemical modified wheat straw in fixed-bed column

Abstract Adsorption of methylene blue (MB) from aqueous solution was studied by natural wheat straw (NWS) and modified wheat straw (MWS) with citric acid in fixed-bed column. The experiments were conducted to investigate the effects of the bed depth, the flow rate, and the influent concentration of MB. The column data were fitted by the Thomas model and Yan model using nonlinear regressive analysis, while bed depth/service time analysis (BDST) model was applied at different bed depths. The Yan and BDST were found suitable for describing the adsorption process. The exhausted adsorbent was regenerated using hydrogen chloride solution and the adsorbent was reused. The results showed that the adsorption capacity of MWS was higher than NWS and both NWS and MWS can be reused.

Adsorption property of methyl orange by chitosan coated on quartz sand in batch mode

AbstractThe adsorption behavior of methyl orange (MO) on chitosan-coated quartz sand (CCS) was studied as a function of initial solution pH, salt concentration, contact time, concentration of MO, and temperature in batch mode. The adsorption quantity of MO on CCS was 45.5 mg g−1 at 293 K under the conditions of pH 4.00, CCS dosage 1.00 g L−1, and contact time 720 min. The high temperature and existence of common salts in solution were disadvantage of MO adsorption. The equilibrium data were fitted well to the Langmuir and Temkin isotherm models. Pseudo-first-order kinetic model, pseudo-second-order kinetic model, Elovich equation, and intra-particle diffusion models were used to fit the kinetic experimental data, and the fitted results showed that Elovich equation was the best to predict the kinetic process. The adsorption was spontaneous and exothermic, according to the thermodynamic parameters. It was concluded that ion exchange occurs mainly in the adsorption process. The dye-loaded adsorbent can be re...

Investigations on the batch performance of cationic dyes adsorption by citric acid modified peanut husk

Abstract A citric acid modified peanut husk (MPH) was used as adsorbent for removal of neutral red (NR) and methylene blue (MB) from aqueous solution. A batch system was applied to study the behavior of NR and MB adsorption in single and binary systems on MPH. Such studies were conducted by varying various parameters such as the initial dye concentration, the pH, the salt concentration, the temperature, and the contact time. Adsorption kinetic data were fitted using pseudo-first-order equation, pseudo-second-order equation, and intraparticle diffusion model. The process mechanism was found to be complex, consisting of both surface adsorption and pore diffusion. The effective diffusion parameter D i values estimated in the order of 10−8 cm2/s indicated that the intraparticle diffusion was not the rate-controlling step. The NR adsorption isotherm follows the Langmuir model, while MB adsorption follows the Freundlich isotherm. The thermodynamics parameters of adsorption systems indicated spontaneous and endo...

Adsorption of Methylene Blue from Aqueous Solution by Wheat Husk in Batch Mode

Wheat husk, an agriculture product, was used to adsorb methylene blue (MB) from aqueous solutions. Variables of the system, including contact time, pH, and equilibrium MB concentration, were adopted to study their effects on MB adsorption. The results showed that as the equilibrium concentration of MB increased, quantity of MB sorption onto wheat husk increased correspondingly. The change of MB adsorbed quantity was very small when the pH was increased from 5.0 to 10.0. The equilibrium data was fitted well by the Langmuir model. The adsorption processes followed the pseudo-second-order rate kinetics. The results in this study indicated that wheat husk was an attractive alternative for removing cationic dyes from the dye wastewater.