Biochar from A Freshwater Macroalga as A Potential Biosorbent for Wastewater Treatment

The multi-elemental composition, surface texture and morphology of biochar, produced by pyrolysis at 300, 350, 400 and 450 degrees C from freshwater macroalga Cladophora glomerata, as a biosorbent of toxic metals was examined with Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. It was found that the yield of pyrolysis was inversely proportional to temperature: for 300 degrees C it was 63%, whereas for 450 degrees C-47%. The proximate analysis revealed that also biochar's moisture and volatile matter was inversely proportional to temperature. The content of ash increased with temperature. All biochars were characterized by a similar total pore area of about 20 m(2) g(-1). FT-IR analysis showed that all biochars peaked at 3500-3100 cm(-1) which was attributed to O-H stretching of the hydroxyl groups, at 2850-2970 cm(-1), stretching vibrations of C-H bonds in aliphatic CH2 and CH groups, at 1605 cm(-1), stretching vibrations from C=C of aromatics, at 1420 cm(-1), bending oscillations from CH2, at about 1111 cm(-1), stretching vibrations of Si-O, at 618 cm(-1), vibrations from Fe-O bonds, and at 475 cm(-1)-Si-O-Si deformation vibrations. The biosorption properties of biochar towards Cr(III) ions were examined in kinetic studies. The biosorption capacity of biochar increased with an increase of pyrolysis temperature: the highest was for biochar obtained at 450 degrees C-87.1 mg Cr(III) g(-1) and the lowest at 300 degrees C-45.9 mg g(-1). Cladophora biochar also demonstrated a good ability to simultaneously remove metal ions from a multi-metal system, e.g., wastewater. The removal efficiency for Cr(III) was 89.9%, for Cu(II) 97.1% and for Zn(II) 93.7%. The biochar derived from waste-freshwater macroalgae can be a potent and eco-friendly alternative adsorptive material.