Sewage sludge and solid residues from biogas production derived biochar as an effective bio-waste adsorbent of fulvic acids from water or wastewater

Due to environmental concern, direct utilization of sewage sludge or residues from biogas production is restricted. Conversion of problematic bio-wastes into biochars can be a very effective solution. In the presented study, the adsorption of fulvic acids onto series of biochars produced from bio-wastes such as sewage sludge, residues from biogas production, and plant (Miscanthus sp.) were performed to examine the behavior of biochars in the environment and interactions with fulvic acids as the representatives of dissolved organic matter. The results clearly indicate that the highest excess of fulvic acids, 93–96 mg g−1, was chemisorbed onto biochar obtained specifically from sewage sludge. The mechanism of the adsorption was independent from applied biochar feedstock. Monolayer coverage was dominant onto all biochars. Generally, adsorption was assumed to be controlled by polar interactions between fulvic acids and the biochars or pre-adsorbed and residual fulvic acids molecules (which were dominant) and the strong π-π interactions. The obtained high values of the adsorption capacity of sewage sludge derived biochars confirmed that thermal treatment is a very effective tool of bio-waste management. [Display omitted] •Conversion of bio-wastes to biochars can solve the problem of their utilization.•Sewage sludge derived biochar has a highest adsorption affinity to fulvic acids.•Rate-limiting step of FA adsorption on tested BC was chemical sorption.•Polar, hydrophobic or strong π-π interactions were dominant.•Bio-waste or biomass derived biochars have similar ability to remove fulvic acids.