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

Abstract

The multi-elemental composition, surface texture and morphology of biochar, produced by pyrolysis at 300, 350, 400 and 450 °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 °C it was 63%, whereas for 450 °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 m2 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 °C—87.1 mg Cr(III) g−1 and the lowest at 300 °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.

Biochars obtained from freshwater biomass—green macroalga and hornwort as Cr(III) ions sorbents

“…To achieve this goal, we focused on the temperature optimization of thermal treatment for the production of biochars and to compare their chemical composition and sorption properties. This work is partly a continuation of our recent research [21], where biochars, obtained from freshwater macroalga Cladophora glomerata in pyrolysis at 300, 350, 400, and 450°C, were successfully applied for Cr(III) ion removal from wastewater-the sorption capacity increased with the increase of pyrolysis temperature and was the highest for 450°C (87.1 mg g −1 ). This observation encouraged us to perform further research that included (i) evaluation of the impact of higher pyrolysis temperatures (> 450°C) on sorption of Cr(III) ions using Cladophora glomerata biochars, (ii) production of biochars derived from another aquatic biomass-hornwort in a wide range of pyrolysis temperatures (250, 300, 400, 500, 600, and 800°C) and examination their sorption properties towards Cr(III) ions.…”

“…A peak at about 470 cm −1 was assigned to Si-O-Si and might be a result of diatoms present within the biomass and was also observed in macroalga biochars (slightly shifted in comparison with peak at 1050 cm −1 observed in hornwort). At 875 cm −1 , a vibration of aromatic C-H bonds was observed for all biochars [21]. For hornwort biochars, until 300°C, a peak of C-H vibrations was observed at about 2930 cm −1 .…”

“…Hornwort biochars were obtained at 250, 300, 400, 500, 600, and 800°C, while macroalga biochars at 500, 600, and 800°C (lower temperatures were studied in our previous research [21]). Pyrolysis was conducted under nitrogen flow of 20 L h −1 .…”

“…Biochars produced from aquatic biomass are mainly used for the removal of toxic metal ions from wastewater [21,22] or as a soil amendment [23,24]. Biochar from freshwater macroalga-Cladophora glomerata was examined as a sorbent of Cr(III) ions [21]; biochar from post-extraction of macroalga residues after oil extraction was used for sorption of Co(II) ions [22]; biochar from water hyacinth was investigated as a sorbent of Zn(II) and Cu(II) ions [25]; biochar from waste marine seaweeds-kelp and hijiki-was applied for sorption of Cd(II), Cu(II), and Zn(II) ions [26]. Hornwort, recognized as an aggressive aquatic weed (pest), easily invades still and flowing waters becoming a dominant species in such basins.…”

Biosorption of zinc from aqueous solution using leaves of Corchorus olitorius as a low‐cost biosorbent

“…Several conventional techniques are used so far, such as—chemical coagulation, ion exchange, and membrane filtration, in this purpose. However, applications of these methods in practical fields have some limitations, as it found to be too expensive and also produce toxic sludge (Incharoensakdi & Kitjaharn, ; Michalak, Basladynska, Mokrzycki, & Rutkowski, ). Therefore, alternate cost‐effective and environment‐friendly methods are being applied in heavy metal remediation process.…”