Zhongmin Wang

Biosorption of palladium(II) from aqueous solution by grafting chitosan on persimmon tannin extract.

A low-cost and environmentally green biosorbent (PTCS) was prepared by grafting chitosan onto persimmon tannin extract and its potentiality for efficient adsorption of palladium ion (Pd(II)) from aqueous solution was evaluated. Various adsorption parameters such as pH, the initial Pd(II) concentration and temperature were investigated. The maximum adsorption capacity reached 330mg/g at 323K and pH 5.0 when the initial Pd(II) concentration was 100mg/L. The equilibrium adsorption data were satisfactorily fitted with Freundlich isotherm model and biosorption kinetics was found to be in good agreement with pseudo-second-order kinetics model. Thermodynamic calculations indicated that the adsorption process was endothermic and spontaneous in nature because of the negative value of free energy change (ΔG) and positive value of enthalpy change (ΔH). The positive value of entropy change (ΔS) revealed the increased randomness at the solid-liquid interface. FT-IR and XRD analysis verified that Pd(II) adsorption on PTCS was electrostatic interaction and redox reaction. Moreover, selective adsorption study revealed that the adsorbent exhibited good adsorption ability to Pd(II) in the mixture metal ions solutions. All these results indicated that the PTCS biosorbent could be used as a low-cost alternative for the adsorption of Pd(II) in waste-water treatment.

Equilibrium, kinetics and mechanism of Au3 +, Pd2 + and Ag+ ions adsorption from aqueous solutions by graphene oxide functionalized persimmon tannin

In this study, a novel bio-adsorbent (PT-GO) was prepared by functionalization persimmon tannin (PT) with graphene oxide (GO) and the effective adsorption behaviors of Au3+, Pd2+ and Ag+ ions from aqueous solution was investigated. The PT-GO was characterized by Fourier transform infrared spectrometer (FTIR), scanning electronic microscope (SEM), thermogravimetric analysis (TGA) and Zeta potential. Many influence factors such as pH value, bio-adsorbent dosage, initial concentration of metal ions and contact time were optimized. The maximum adsorption capacity for Au3+, Pd2+ and Ag+ was 1325.09mg/g, 797.66mg/g and 421.01mg/g, respectively. The equilibrium isotherm for the adsorption of Au3+ and Ag+ on PT-GO were found to obey the Langmuir model, while the Freundlich model fitted better for Pd2+. The adsorption process of Au3+, Pd2+ presented relatively fast adsorption kinetics with pseudo-second-order equation as the best fitting model, while the pseudo-first-order kinetic model was suitable for describing the adsorption of Ag+. Combination of ion exchange, electrostatic interaction and physical adsorption was the mechanism for adsorption of Au3+, Pd2+ and Ag+ onto PT-GO bio-adsorbent. Therefore, the PT-GO bio-adsorbent would be an ideal adsorbent for removal of precious metal ions and broaden the potential applications of persimmon tannin in environmental research.

Adsorption of Ag+ by persimmon tannins immobilized on collagen fiber

AbstractIn the present work, a novel adsorbent to effectively adsorb Ag+ from an aqueous solution has been prepared by immobilizing persimmon tannin (PT) on collagen fiber. The adsorption capacity of Ag+ on the immobilized PT were evaluated under various treatment conditions, including the initial solution pH, solid–liquid ratio, temperature, and initial concentration of Ag+. The results showed that the effect of initial solution pH, solid–liquid ratio, and initial concentration of Ag+ on the adsorption capacity were remarkable, while the influence of temperature was insignificant. The adsorption capacity reached 1947 mg/g at 303 K and pH 7.0 when the initial concentration of Ag+ was 800 mg/L and solid–liquid ratio was 0.4. Adsorption equilibrium isotherms of Ag+ on the surface of the adsorbent fibers were studied using Freundlich and Langmuir isotherms. The experimental data fitted best to the Freundlich models. Also, the immobilized PT before and after adsorption of Ag+ was characterized by Fourier tran...

Preparation and characterization of a novel polyethyleneimine cation-modified persimmon tannin bioadsorbent for anionic dye adsorption

A novel and recyclable bioadsorbent (PTP) has been prepared by the cationization of persimmon tannin (PT) using polyethyleneimine (PEI) for application in the removal of the anionic dye methyl orange (MO) from aqueous solution. The physicochemical properties of the prepared PTP were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, Zeta potential measurements, Brunauer-Emmett-Teller and thermogravimetric analysis. Systematic batch adsorption experiments were carried out with pH, bioadsorbent dosage, initial MO concentration and contact time. Kinetic regression analysis indicated that the adsorption processes followed the pseudo-second order model. The equilibrium isotherm was in good fit with the Freundlich model with a maximum adsorption capacity of 225.74 mg/g. Thermodynamics data revealed that the adsorption of MO onto PTP was feasible, spontaneous and endothermic. A possible biosorption mechanism was presented where electrostatic interactions, hydrogen bonding, and π-π interactions dominated the adsorption of MO onto PTP. Moreover, the regeneration of the PTP was easily achieved and MO removal efficiency remained high (81.47%) after six cycles. The actual sewage treatment simulation was evaluated and the PTP had a good preference to adsorption MO. All these results indicated that PTP could be considered a high performance and promising candidate for the effective removal of anionic dyes from aqueous solutions.

Chitosan modification persimmon tannin bioadsorbent for highly efficient removal of Pb(II) from aqueous environment: the adsorption equilibrium, kinetics and thermodynamics

ABSTRACT Lead (Pb) pollution has triggered a great threat to ecological system as well as public health due to its highly toxic and mutagenic properties. In this study, chitosan surface modified persimmon tannin (PT-CS) biomass composite as an environmental-friendly bioadsorbent for highly efficient removal of Pb(II) from aqueous solutions was investigated. Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscope, Brunauer–Emmett–Teller, X-ray photoelectron spectroscopy and Zeta potential were used to elucidate the adsorption mechanism. Combining oxidation reaction, electrostatic interaction and chelation reaction, PT-CS exhibited fine adsorption to Pb(II). The maximum adsorption capacity was 179.3 mg/g. Equilibrium isotherm for the adsorption of Pb(II) was analyzed by the Langmuir, Freundlich and Temkin models, and the Langmuir isotherm (R2 > 0.99) was the best. The pseudo-first-order, pseudo-second-order and intraparticle diffusion equations were used to analyze the kinetic data of the adsorption process and the pseudo-second-order kinetic (Rs2 > 0.98) model was fitted well. Moreover, thermodynamic parameters including ΔG0 < 0, ΔH0 (150.57 KJ/mol) > 0 and ΔS0 (456.13 J/mol K) > 0 showed that the process of Pb(II) adsorption by PT-CS was spontaneous and endothermic. All these results illustrated that PT-CS would be a promising and low-cost alternative bioadsorbent of Pb(II) in wastewater treatment. GRAPHICAL ABSTRACT