Humic Substances Extracted from a Bio-stabilized Waste Applying Different Operating Conditions

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ORIGINAL PAPER

Humic Substances Extracted from a Bio‑stabilized Waste Applying Different Operating Conditions Daniela Zingaretti1   · Alessio Lieto1 · Francesco Lombardi1 · Renato Gavasci1 Received: 30 October 2019 / Accepted: 29 April 2020 © Springer Nature B.V. 2020

Abstract  Humic substances are the major constituents of the organic matter of soils and sediments and were adopted in different industrial applications for their high content of functional groups. Recently, the research interest is focused on the possibility of extract these substances also from organic wastes, such as biowastes. However, an interesting option could be to extract humic substances from other organic stabilized wastes that differently from compost has no further use. Namely, in this study the possibility of extract Humic Acids (HA) from the bio-stabilized waste produced from a Mechanical Biological Treatment plant adopting different maturation durations was evaluated. Furthermore, the effect of the main operating conditions applied during the alkaline extraction of the humic acids was also investigated (i.e. material particle size, liquid–solid ratio, NaOH concentration and extraction time), analysing the elemental composition, the main functional groups content and the optical properties of the extracted HA. The operating conditions that showed to improve the extraction extent were the NaOH concentration and the extraction time. Furthermore, the HA obtained in these specific conditions showed higher functional groups content and aromaticity, in agreement with the characteristics of the commercial HA, allowing to consider these substances for various industrial applications. Graphic Abstract Biostabilised Waste (BSW)

Extract SOLUBLE BIORGANIC SUBSTANCES

ACIDIFICATION (pH < 2)

g HA/kg BSW

60

ALKALINE EXTRACTION (65 °C, N2)

Solid residue (HUMIN)

70

NaOH

50

40 30 20 10 0

Precipitate HUMIC ACIDS (HA)

Liquid FULVIC ACIDS (FA)

A

B

C

D

E

Keywords  Humic substances · Bio-stabilized waste · Maturation · Alkaline extraction · Humification * Daniela Zingaretti [email protected]

Statement of Novelty

1

This work provide new insights about the effect of operating conditions on the extraction yields and the chemical properties of the humic acids extracted from bio-stabilized waste



Laboratory of Environmental Engineering, Department of Civil Engineering and Computer Science Engineering, University of Rome “Tor Vergata”, Via del Politecnico 1, 00133 Rome, Italy

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(BSW) produced from a Mechanical Biological Treatment (MBT) plant.

Introduction Humic substances are non-living natural organic matter (NOM), derived from the residues of dead plants, animals, microorganisms and their degradation products and persist in all natural environments [1]. These substances are brown to dark colored mixtures of complex organic compounds that are usually separated into three different fractions: (a) fulvic acids (FAs), soluble in water under all pH conditions; (b) humic acids (HAs), insoluble in acidic water