Pulp mill sludge-derived carbon activated with an alternative source of chemicals and its application in wastewater treatment – An approach for byproducts valorization

• Published in: Journal of environmental management Vol. 298; p. 113477
• Main Authors: Oda, Tatiana Yuri Ramos, Rezende, Ana Augusta Passos, Sousa, Rita de Cássia Superbi, Silva, Cláudio Mudadu, Pereira, Alex Cardoso
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 15.11.2021
• Subjects: Adsorption wastewater treatment; Alternative adsorbents; Biological sludge; Circular economy; Tertiary treatment of effluents; Waste-to-resource; Tertiary treatment of effluents; Waste-to-resource; Circular economy; Alternative adsorbents; Adsorption wastewater treatment; Biological sludge
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2021.113477

The purpose of this study was to investigate pulp mill by-products valorization through activated carbon (AC) production and its application in wastewater treatment. Bio-sludge is a known promising precursor for AC production. The mill's chemical recovery stage generates an effluent (electrostatic precipitator ash leachate - EPAL) with high levels of potassium and sodium, which motivate studies regarding its viability as a chemical source for carbon activation. Bio-sludge and EPAL are problematic by-products and this research line would allow their return to the productive chain, as an adsorbent for the wastewater treatment. Two carbonization heating rates (3.5, 15 °C/min), three activation agents (NaOH, KOH, EPAL) and two activator:bio-sludge ratios (1:1, 2:1) were used for AC production. The best ACs in terms of surface area were those produced at 3.5 °C/min, with KOH or EPAL in 2:1 proportion. ACs produced under these conditions and commercial activated carbon (CAC) were used in adsorption tests with industrial wastewater. For color removal, KOH-activated carbon presented the greatest efficiency (80.45 %), followed by CAC (76.74 %) and EPAL-activated carbon (70.13 %). For COD removal, EPAL-activated carbon presented greater efficiency (53.49 %), followed by CAC (40.84 %) and KOH-activated carbon (36.86 %). Freundlich's model best described the experimental adsorption data. The KOH results were expected to be satisfactory, since KOH is proven to be effective for carbon activation. The EPAL-activated carbon results were remarkable, especially for COD removal, showing that EPAL can be used as an activator and that the by-products have potential for valorization according to the circular economy principles. [Display omitted] •Problematic byproducts management was applied according to circular economy concept.•Electrostatic precipitator ash leachate (EPAL) was effective for carbon activation.•Heating rate, activator and proportion were significant for adsorbent production.•The maximum color removal efficiency was 80.45 % with KOH-activation.•The maximum COD removal efficiency was 55.85 % for EPAL-activation.