Biochar from co-pyrolysis of biological sludge and woody waste followed by chemical and thermal activation: end-of-waste procedure for sludge management and biochar sorption efficiency for anionic and cationic dyes

• Published in: Environmental science and pollution research international Vol. 31; no. 24; pp. 35249 - 35265
• Main Authors: Bakari, Zaineb, Fichera, Michelangelo, El Ghadraoui, Ayoub, Renai, Lapo, Giurlani, Walter, Santianni, Daniela, Fibbi, Donatella, Bruzzoniti, Maria Concetta, Del Bubba, Massimo
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.05.2024; Springer Nature B.V
• Subjects: Activated carbon; Adsorption; Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Cationic dyes; Charcoal; Charcoal - chemistry; Chemical treatment; Coloring Agents - chemistry; Design of experiments; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental Health; Gasification; Methylene blue; Municipal wastewater; Polycyclic aromatic hydrocarbons; Pyrolysis; Research Article; Sawdust; Sewage - chemistry; Sewage sludge; Sludge; Sorption; Waste Disposal, Fluid - methods; Waste Water Technology; Wastewater; Water Management; Water Pollution Control; Water treatment; Wood - chemistry; Direct yellow 50; Biochar production; Column experiments; Biochar characterization; Design of experiment; Isotherm experiments; Industrial wastewater remediation; Methylene blue
• ISSN: 1614-7499; 0944-1344; 1614-7499
• DOI: 10.1007/s11356-024-33577-3

Nine biochars were produced by co-pyrolysis of sawdust and biological sludge following the “design of experiment” approach. Two kinds of sludge (both deriving from the treatment of mixed industrial-municipal wastewater) and two types of woody waste were selected as categorical predicting variables, while contact time, pyrolysis temperature, and sludge percentage were used as quantitative variables. Biochars were analysed for their product characteristics and environmental compatibility based on the European Standards (EN 12915–1:2009) for materials intended for water treatment (i.e. ash content, water leachable polycyclic aromatic hydrocarbons (PAHs) and elements), as well as for specific surface area (SSA), using them as response variables of a multivariate partial least square multiple regression, whose results provided interesting insights on the relationships between pyrolysis conditions and biochar characteristics. Biochars produced with sludge and/or providing the highest SSA values (258–370 m 2  g −1 ) were selected to undergo a sustainable chemical treatment using a by-product of the gasification of woody biomass, complying in all cases with European Standards and achieving therefore the end-of-waste status for sewage sludge. The biochar deriving from the highest percentage of sludge (30% by weight) and with the highest SSA (390 m 2  g −1 ) was thermally activated achieving SSA of 460 m 2  g −1 and then tested for the sorption of direct yellow 50 and methylene blue in ultrapure water and real wastewater, compared to a commercial activated carbon (AC). The biochar showed Langmuir sorption maxima ( Q m ) 2–9 times lower than AC, thus highlighting promising sorption performances. Q m for methylene blue in wastewater (28 mg‧g −1 ) was confirmed by column breakthrough experiments.