Green Synthesis of Tannin-Polyethylenimine Adsorbent for Removal of Cu(II) from Aqueous Solution

Abstract

In this work, the adsorbent based on tannin (TN) and polyethylenimine (PEI) was prepared via a simple and green method (TNP). The characteristics of the TNP were determined using scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, and the results revealed that TNP was synthesized by TN and PEI, and Cu(II) was combined with the −NH or −OH groups of TNP. The effects of the n (TN) :n (PEI) , adsorbent dosage, pH, time, initial metal concentration, and temperature on the adsorption of Cu(II) were investigated in detail. The adsorption of Cu(II) by TNP was greatly affected by pH, and n (TN) :n (PEI) = 1.5:3 was the optimum mole ratio of raw material to obtain TNP. TNP possessed excellent adsorption properties, and the maximum adsorption capacity of TNP for Cu(II) was 94.5 mg/g at 338.15 K. The adsorption process was in agreement with the Langmuir model and the pseudo-second-order model. Regeneration and reusability of TNP did not decrease significantly after four times of regeneration experiments. The order of competitive ability for the three metal ions was as follows: Pb(II) > Cu(II) > Zn(II). These experimental results suggested that TNP could effectively remove metal ions from aqueous solution. This study is of great significance for environmental protection.