Lead (Pb2+) sorptive removal using chitosan-modified biochar: batch and fixed-bed studies

Chitosan-Modified fast pyrolysis BioChar (CMBC) was used to remove Pb2+ from water. CMBC was made by mixing pine wood biochar with a 2% aqueous acetic acid chitosan (85% deacylated chitin) solution followed by treatment with NaOH. The characterizations of both CMBC and Non-Modified BioChar (NMBC) were done using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), scanning electron microscopy (SEM), surface area measurements (S-BET), elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and -potential measurements. Elemental analysis indicated that chitosan accounts for about 25% weight of the CMBC. The Langmuir maximum adsorption capacity of CMBC at pH 5 was 134 mg g(-1)versus 48.2 mg g(-1) for NMBC at 318 K. CMBC column adsorption studies resulted in a capacity of 5.8 mg g(-1) (Pb2+ conc. 150 mg L-1; pH 5; column dia 1.0 cm; column length 20 cm; bed height 5.0 cm; flow rate 2.5 mL min(-1)). CMBC removed more Pb2+ than NMBC suggesting that modification with chitosan generates amine groups on the biochar surface which enhance Pb2+ adsorption. The modes of Pb2+ adsorption on CMBC were studied by comparing DRIFTS and X-ray photoelectron spectroscopy spectra before and after Pb2+ adsorption.