Comparative investigation on removal characteristics of tetracycline from water by modified wood membranes with different channel walls

Abstract

The alkali-innocuous citric acid (CA) modified wood membranes (WMs) have been developed as facile, economical, and effective adsorption membranes to remove tetracycline (TC) from water. However, TC removal by modified WMs with different types of wood channel walls have rarely been compared. Therefore, in this study, modified WMs were prepared with pinewood (PW) and basswood (BW). The PW and BW WMs before and after modification were characterized by SEM, EDX, XRD, ATR-FTIR, TGA, contact angle and zeta potential. After modification, cellulose I in cellulose crystal structures of raw WM transformed to cellulose II and the contents of carboxylic groups for PW and BW were enhanced to make the hydrophilicity of WM surface increased. Compared with modified PW WMs, particles formed on the channel walls of modified BW WMs containing vessel pits to make more carboxylic groups introduced. The TC adsorption breakthrough curves showed that the 6 wt% alkali- CA modified BW had an effective filtration volume of 1968 bed volume (BV) compared with the 4 wt% alkali-CA modified PW of 1205 BV as the influent TC and breakthrough point were chosen at 2 and 0.5 mg/L, respectively. At low pH, TC complex with WM surfaces through Lewis acid-base interaction. Zwitterionic TC was shown to favor adsorption onto WM via hydrogen bonding at pH of around 5. With further increasing pH, TC adsorption efficiency decreased due to the electrostatic repulsion. The costs of modified BW and PW are about 0.0054–0.0126 US$/m3 and 0.01–0.024 US$/m3 for a low TC concentration effluent (0–0.5 mg/L), respectively. This work shed a new sight on how to develop economical and effective adsorption WMs for contaminants removal from water.