Microwave-assisted synthesis of esterified bacterial celluloses to effectively remove Pb(II)

Abstract

Two modified bacterial celluloses, xanthate-modified bacterial cellulose (XMBC) and sulfate-modified bacterial cellulose (SMBC), were prepared from bacterial cellulose (BC) esterified with xanthate and sulfate, respectively, using microwave irradiation. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy, and Brunauer-Emmett-Teller (BET) surface analysis. Batch experiments were carried out to determine the ability of XMBC and SMBC to remove Pb(II) from solution. The effects of pH, contact time, temperature, initial adsorption concentration, and ionic strength on Pb(II) removal were investigated along with regeneration performance. Both the specific surface area and total pore volume of the modified biosorbents were higher than those of unmodified bacterial cellulose. The adsorption of Pb(II) decreased with increasing temperature and ionic strength, and the optimal pH was 5.0. The introduction of thiol groups on bacterial cellulose increased its adsorption capacity for Pb(II); the modified biosorbents exhibited adsorption capacities of 144.93 mg•g-1 for XMBC and 126.58 mg•g-1 for SMBC. The adsorption rate closely followed a pseudo-second order model and the adsorption isotherm data were consistent with the Langmuir model. The adsorption of Pb(II) was exothermic, and the spent adsorbents could be readily regenerated for reuse. As a result, SMBC and XMBC are promising materials for the preconcentration and separation of heavy metals from large volumes of aqueous solutions.