Sorption of α-, β-, γ- and δ-hexachlorocyclohexane isomers to three widely different biochars: Sorption mechanisms and application

Abstract

Within this study different biochars (BC) with widely varying characteristics have been tested as materials for the adsorption of hexachlorocyclohexane's (HCH) isomers (α, β, γ and δ) from water. Three BCs produced from digestate (700 ºC), greenhouse tomato waste (550 ºC) and durian shell (400 ºC) were tested. The BCs demonstrated variable physico-chemical characteristics, especially with respect to surface area, with CO 2-surface area ranging from 5.4 to 328.6 m 2 g-1 and iron content ranging from 0.0733 to 11.17 g kg-1. Isotherm tests were carried out to understand which mechanisms drive HCH uptake to BC, to assess whether stereochemistry affects adsorption and to assess whether competitive sorption occurs. Log K F values ranged from 3.7 to 5.8 (µg kg-1) (µg L-1)-n for the various isomers on the three biochars. No competition (t-test, P < 0.0001) was observed between α-, β-, γand δ-HCH. Freundlich adsorption constants of α-, γand δ-HCH followed the order: BC digestate > BC greenhouse tomato waste > BC durian shell, in contrast to β-HCH which followed the order: BC durian shell > BC greenhouse tomato waste > BC digestate. In addition to stereochemistry, sorption

A Review of Non-Soil Biochar Applications

“…They showed that surface amination and oxidation can improve biochar adsorption properties. Furthermore, polyhalogenated hydrocarbons were removed from waste stream by using biochar that was produced from the pyrolysis of digestate with an uptake of up to 11 mg/g [150].…”

HCH Removal in a Biochar-Amended Biofilter

“…Biochar, a charcoal produced from plant biomass, is an inexpensive and renewable adsorbent that has been used for a variety of applications, including soil conditioning and remediation, carbon sequestration, water treatment and the absorption of a variety of pollutants [17]. However, although biochar is rapidly gaining in popularity, only a limited number of studies have been published on the use of biochar for minimizing the bioavailability of pollutants, most of which have been laboratory based [18][19][20][21], and most concentrating on the factors affecting its ability to remove organic pollutants [22,23]. One exception was a recent study that sought to restore sediments contaminated by γ-HCH and hexachlorobenzene through amendment with carbon-rich materials, with the aim of sequestering the contaminants and rendering them biologically unavailable [24].…”