Abstract:
Partially treated wastewater released into natural water bodies leads to eutrophication which poses a threat to
aquatic animals and water supply security. The recovery of nutrients from wastewater, and their subsequent
recycling in other agricultural applications contribute to nutrient recycling and utilization. Biochar derived from
biomass waste is increasingly seen as a multifunctional material for the adsorption of various pollutants from
wastewater. This is due to its low production cost and carbon footprint. Recycled paper waste sludge (RPWS)
is another abundant type of woody biomass that yields biochar as a by-product during pyrolysis processes. This
material has emerged as a feedstock to produce several liquid fuels such as bio-oils and alcohols. However,
there has been little application of the material as an adsorbent for the removal of nutrients and pollutants from
wastewater. Two variants of RPWS were available for this work, primary sludge from screening processes and
secondary sludge from a clarification plant were used as feedstocks to produce biochar products via slow
pyrolysis at 550 °C, and 650 °C. Furthermore, a step to produce magnetic biochar was added through
impregnation with Fe3+ and Fe2+ and subsequent co-pyrolysis. The biochar yields are promising for the pyrolysis
of RPWS. The structural analysis and morphological characterization of the samples (before and after pyrolysis)
were done through thermogravimetric analysis (TGA), Scanning Electron Microscopy (SEM-EDS), Fourier
Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Brunauer-Emmet Teller (BET). The
residues after pyrolysis showed good physical and chemical qualities that can be beneficial for the adsorption
of nutrients in wastewater treatment.
