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The adsorptive removal of nickel by persimmon tannin-based adsorbents was first evaluated. NaOH modified persimmon powder-formaldehyde resin (NPPFR) showed significantly enhanced adsorption capacity towards Ni(II). The adsorption process was completely achieved equilibrium within 60 min, and the well-fitted pseudo-second-order kinetics data indicated that chemisorption is the main rate-limiting step. The adsorption isotherms followed the Langmuir model, where the maximum adsorption capacity reached 81.6 mg g–1 at pH 5.0. The adsorbed Ni(II) ions were desorbed by 0.1 mol L–1 HNO3 and the regenerated adsorbent exhibited undiminished sorption efficiency for 4 cycles. The removal of Ni(II) from actual industrial wastewaters in both batch and column experiments was demonstrated to be effective. The adsorption mechanism was proposed to be electrostatic attraction and ion exchange. In addition, competition and replacement during the adsorption process were found in the multiple metal ions systems. The results indicated that NPPFR can serve as a low-cost, eco-friendly and effective alternative for Ni(II) removal in wastewater treatment. [ABSTRACT FROM AUTHOR]

A new and green tannin rigid foam was prepared without using formaldehyde and named as "Kaki-TRF" since the tannin is derived from waste persimmon (Diospyros kaki Thunb.) barks. Persimmon tannin is highly reactive and the cross linker is not necessary. The prepared foam was of porous nature and the Brunauer-Emmett-Teller (BET) surface area is 7.014 m? g-1. Adsorption of Au(III) ions from aqueous solution by Kaki-TRF was investigated including the effect of solid-liquid ratio, initial pH, reaction time, initial concentration of Au(III) and ionic strength. The selective property of Kaki-TRF toward Au(III) was examined in both static and continuous adsorption manners. Pseudo-second-order and Langmuir can well fit the experimental data of adsorption kinetics and isotherms. The calculated maximum adsorption capacity of Kaki-TRF toward Au(III) is 1.31 mmol g-1 which is relatively high compared with other porous bio-sorbents. Electrostatic attraction and in situ reduction were proposed to be the main adsorption mechanisms. The adsorption-regeneration recycling test proved that Kaki-TRF can be reused for at least five times. [ABSTRACT FROM AUTHOR]