Sustainable N-containing biochars obtained at low temperatures as sorbing materials for environmental application: Municipal biowaste-derived substances and nanosponges case studies

The impact of hydrothermal carbonization on the surface functionalities of wet waste materials for water treatment applications

“…Results from this study were in line with previous studies made with similar materials, such as pyrolyzed sludge (24 mg g −1 ), granular sludge ZnCl 2 activated biochar (91 mg g −1 ), biochar/AlOOH nanocomposite (85 mg g −1 ), coffee husk hydrochar (35 mg g −1 ), and composted biowaste pyrochar (15 mg g −1 ) (Anceschi et al 2018;Fan et al 2017;Ronix et al 2017;Shi et al 2014;Zhang and Gao 2013) while the removal capacities for commercial activated carbons may vary from a few hundred milligrams to nearly a thousand milligrams per gram of carbon (Rafatullah et al 2010).…”

Thermal Conversion of Municipal Biowaste Anaerobic Digestate to Valuable Char

“…The surface charge of MWDF char was evaluated by performing a ζ potential measurement at constant pH, temperature, and ionic strength, highlighting the formation of strongly negatively charged surfaces (see Table 1) useful for developing interactions with positive substrates. This behavior is in agreement with the literature for analogous systems [7,21].…”

“…As expected, with respect to the pristine MWDF, pyrolysis leads to a significant increase in the %C (from 54.5% to 72.7%) and a drastic reduction of the %H (from 6.2% to 2.2%), thus confirming the carbonization reaction. The heteroatom content (%N), as already evidenced in our previous study [7], remains almost constant during the thermal process (from 7.5% to 7.2%). This phenomenon could be attributed to a progressive inclusion of nitrogen species into cycloaliphatic and/or aromatic structures, forming a N-containing char.…”

“…1520 cm −1 ) [19]. The char produced by pyrolysis treatment at 540 • C, instead, confirmed the carbonization process of MWDF, with the loss of the polar functionalities and the incipient formation of a broad signal in the 1600-1000 cm −1 range due to the presence of C-C and C=C groups [7].…”

“…The authors of this work have already carried out previous studies [7][8][9] on the pyrolysis of several types of biowaste from both animal and vegetal sources. The pyrolysis of the MBW anaerobic digestate has not been reported yet.…”