Impact of biochar physical properties on adsorption mechanisms for removal of aromatic aqueous contaminants in water
Griffin Loebsack, Ken K.‐C. Yeung, Franco Berruti, Naomi B. Klinghoffer
Abstract
A potential application of biochars produced by pyrolysis of lignocellulosic feedstocks is as sustainable adsorbent materials for the removal of organic contaminants in water, such as pharmaceuticals and dyes. To understand the impact of biochar's physical characteristics on the adsorption mechanisms of organic aromatic contaminants in water, Douglas fir and red cedar derived biochars were produced and treated under different conditions. CO 2 was found to produce biochar with greater oxygen-containing functional groups and higher aromaticity compared to those produced under N 2, while the pyrolysis temperature showed greater adsorption for organic contaminants when pyrolyzed at higher temperatures, attributed to greater aromaticity and surface area. The effect of different oxygen-containing groups, mainly on π - π interactions was explored by characterizing the biochar surface after three different post-pyrolysis treatments (HNO 3 , H 2 O 2 , and KOH) and comparing the effects on the adsorption mechanisms for test compounds (ibuprofen, acetaminophen, methyl orange, and methylene blue). The results showed that increasing aromaticity and electron-donating groups, such as hydroxyl functional groups, increased π - π electron donor-acceptor (EDA) interactions with compounds containing electron-withdrawing groups. The presence of electron-withdrawing carbonyl groups resulted in an increase in adsorption towards compounds with electron-donating groups. • Biochar is investigated for adsorption of organic pollutants from wastewater. • Biochar surface was modified by KOH, H 2 O 2 , HNO 3 to elucidate adsorption mechanisms. • Biochar surface oxygen groups impact adsorption mechanisms due to π - π interactions. • Electron-withdrawing carbonyl groups adsorb compounds with electron-donating groups. • Hydroxyl groups result in π - π and electrostatic interactions with pollutants.