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Activated carbon from kraft lignin: A sorbent for in situ remediation of contaminated sediments

Research paper by Åsa Gustafsson, Sarah Hale, Gerard Cornelissen, Elisabeth Sjöholm, Jonas S. Gunnarsson

Indexed on: 18 Nov '16Published on: 17 Nov '16Published in: Environmental Technology & Innovation



Abstract

A new type of activated carbon derived from Kraft lignin, separated from black liquor in the paper pulp process, was evaluated for its use as an alternative sorbent to commercial powdered activated carbons (AC) from anthracite (<img height="14" border="0" style="vertical-align:bottom" width="46" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si16.gif">ACCOAL) or coconut (<img height="14" border="0" style="vertical-align:bottom" width="36" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si17.gif">ACBIO) for remediation in situ   of contaminated sediments. Two types of kraft lignins (KL): (1) softwood (SKL), (2) hardwood (HKL) were first evaluated for their sorption to PAHs using assays in water with passive samplers (POMs). Results showed that without further chemical modifications the two kraft lignins tested had lower sorption coefficients than commercial <img height="14" border="0" style="vertical-align:bottom" width="46" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si16.gif">ACCOAL or <img height="14" border="0" style="vertical-align:bottom" width="36" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si17.gif">ACBIO and are not good sorbents for remediation. Following these initial tests a new type of AC derived from softwood (<img height="14" border="0" style="vertical-align:bottom" width="38" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si15.gif">ACSKL) was for the first time produced in the lab using activation with potassium hydroxide (KOH) (lignin:KOH, 1:3 by dry weight) and pyrolysis at 700 °C. Sorption properties of the new <img height="14" border="0" style="vertical-align:bottom" width="38" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si15.gif">ACSKL was compared to the other ACs in water spiked with PAHs and in water with PAH-contaminated sediment. Sorption results were also compared to bioavailability measurements, using digestive fluid extraction (DFE) in vitro  , a method that mimics the solubilization of contaminants that occurs in the gut of a sediment-ingesting invertebrate. <img height="14" border="0" style="vertical-align:bottom" width="38" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si15.gif">ACSKL was found to have similar surface area, pore volume and sorption coefficients as <img height="14" border="0" style="vertical-align:bottom" width="46" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si16.gif">ACCOAL and <img height="14" border="0" style="vertical-align:bottom" width="36" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si17.gif">ACBIO and thus offers a new potential sorbent for remediation, based on a more renewable biomass-derived source than AC from coal. Sediment amendment with 1% <img height="14" border="0" style="vertical-align:bottom" width="38" alt="View the MathML source" title="View the MathML source" src="http://origin-ars.els-cdn.com/content/image/1-s2.0-S2352186416301377-si15.gif">ACSKL reduced the bioavailability of PAHs on average by 56% (measured by DFE) compared to reduced pore water concentrations by 21% (measured with passive samplers). Our results show that a new type of AC based on softwood kraft lignin, a renewable and locally produced biomass material, could be used as an alternative sorbent for sediment and water remediation provided it is produced in sufficient amount and at a competitive price compared to other traditional ACs.

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