Surface Charge Effects on Adsorption of Solutes by Poplar and Elm Biochars

Steven C Peterson,Sanghoon Kim,Jason Adkins

doi:10.3390/c7010011

Abstract

Elm and poplar are two tree species that can provide a large amount of low-value feedstock for biochar production due to their rapid growth rate (poplar), and susceptibility to disease and/or infestation (both elm and poplar). Biochar has been studied recently as filtration medium for water purification, as it provides a renewable alternative to activated carbon. In this work, the adsorption efficiency of biochars made from elm and poplar as a function of pyrolysis temperature were studied by ultraviolet (UV) adsorption of dyes with positive, neutral, and negative charges to determine what factors had the greatest effect on adsorption of these dyes. It was found that conductivity of the biochars increased with pyrolysis temperature, and that this factor was more important than surface area in terms of adsorbing charged dyes. Both elm and poplar biochars were not effective in adsorbing neutral dyes. This research demonstrates that elm and poplar biochars adsorb charged (either positively or negatively) solutes more efficiently than uncharged ones because they carry both charges themselves. Therefore, these biochars would make excellent candidates as renewable filtration media for charged contaminants.

Highlights

Adsorption of Solutes by Poplar and Biochar is a form of charcoal that can be made from biomass; it is defined as the solid, carbon-containing material that results from the thermochemical treatment of biomass in the absence of oxygen [1]
Carbon content for these biochars is very high, ranging from 86% to nearly 97% carbon, with carbon content generally increasing with pyrolysis temperature
Most biochars will see an increase in the percent carbon content as pyrolysis temperature is increased due to increasing loss of volatile components of the feedstock [23]

Summary

Introduction

Adsorption of Solutes by Poplar and Biochar is a form of charcoal that can be made from biomass; it is defined as the solid, carbon-containing material that results from the thermochemical treatment of biomass in the absence of oxygen [1]. Since wood biochar is both carbon-containing and porous, this makes it an excellent candidate for water filtration applications and this is an active area of research [4,5,6,7]. Elm and poplar are two species of trees native to the United States that are both susceptible to disease/infestation via Dutch elm disease [12] and outbreaks from tent caterpillars and gypsy moths [13], respectively. Healthy poplar trees are a rapidly growing species that flourishes in Canada and the northern United States from the Great Lakes region eastward to New England. As a result of both disease and the rapid growth rate of poplar, these two tree species generate massive amounts of low-value wood annually. Low value elm and poplar wood make excellent feedstock for biochar in this application

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Conclusion