Temperature and pH responsive cellulose filament/poly (NIPAM-co-AAc) hybrids as novel adsorbent towards Pb(II) removal.

A novel thermo- and pH sensitive adsorbent, composed of cellulose filament (CF) as the reinforcement scaffold and crosslinked copolymer of, N-isopropylacrylamide (NIPAM) as the thermosensitive component and acrylic acid (AAc) as the pH sensitive component was prepared. SEM images indicated the formation of semi-interpenetrating network between CF and poly(NIPAM-co-AAc). FTIR spectra displayed the characteristic peaks for CF and poly(NIPAM-co-AAc). DSC reflected the lower critical solution temperature derived from PNIPAM in the hybrids. The swelling ratios exhibited dependence on temperature and pH. The adsorption of Pb(II) on CF/poly(NIPAM-co-AAc) reflected pH-dependence. The adsorption kinetics followed a pseudo-second-order model. At 293 K, the maximum adsorption capacity of CF/poly(NIPAM-co-AAc) was 80.8 mg/g, higher than that of CF (45.6 mg/g) as reflected by kinetics curves. Furthermore, with temperature variation, stepwise adsorption-and-halt behavior was observed at pH 6.0, while swing desorption behavior could be observed at approximately pH 3.0.