Graphitic bio-char and bio-oil synthesis via hydrothermal carbonization-co-liquefaction of microalgae biomass (oiled/de-oiled) and multiple heavy metals remediations

Thermochemical transformation of microalgae biomass into graphitic bio-chars entices as proficient bioadsorbents for heavy metal contaminants. This study explores the synergistic impact of Chlorella sorokiniana on biomass generation and wastewater remediation in high rate algae pond (HRAP). Biomass produced was applied for hydrothermal carbonization-co-liquefaction (HTCL). The structural and morphological characteristics of HTCL products (i.e. bio-chars and bio-oils) have been systematically studied by XRD, Raman, FTIR, elemental analyzer, SEM, BET, and H-1 NMR spectroscopy. The crystallite size of the graphite 2H indexing planes was to be 4.65 nm and 14.07 nm in the bio-chars of oiled biomass (MB-0B) and de-oiled biomass (MB-DOB), respectively. The increase in the I-D/I-G ratio of MB-DOB indicated the highly disordered graphitic structure due to the appearance of carbonyl, hydroxyl, and epoxy functionalities in the line of high C/N and low C/H ratio. Also, the multiple heavy metals remediation of MB-DOB revealed better efficiency as similar to 100% in 720 min. The kinetics analysis shows the correlation coefficient of pseudo-second-order is well fitted compared to the pseudo-firstorder. The Langmuir adsorption model signifies the adsorption of heavy metal ions in a monolayer adsorption manner. The study proposes the microalgae bio-char potential for multiple heavy metals remediation alongside bio-oils.

Automated summary

This study demonstrates the synergistic impact of Chlorella sorokiniana on biomass generation and wastewater remediation using high rate algae pond (HRAP). The bio-chars produced through hydrothermal carbonization-co-liquefaction showed efficient heavy metal remediation abilities, with structural characteristics favorable for metal adsorption.