Boreal peatlands play critical roles in carbon sequestration and water retention in North America cold regions, with more than 2.8 % of global lands occupied by peats. Droughts are frequent precursors to peat fire, and their extensive occurrence in boreal forests often lead to hydrophobic peat layers, which can cause surface runoff and soil erosion. Excavation of the hydrophobic pre- and post-fire peats can resolve this problem. Here we have developed a single-step method to turn these abundant bio-materials into value-added activated carbons, which employs ZnCl<sub>2</sub> impregnation and heat treatment at 400 or 600 °C under inert N<sub>2</sub> flow. The produced porous carbon sorbents can readily adsorb a model phenolic compound, p-nitrophenol, from wastewater. These activated carbons were compared against those made from corn starch and cellulose, two other widely available bioproducts with simpler organic composition. Porous carbons were characterized by elemental analyses, zeta potential, BET, FTIR, XPS, XRD and SEM. Boreal peat sorbents exhibit micro- or mesopore properties, and have amorphous carbons, aromatic ethers, esters, alcoholic and phenolic groups. 600 °C produced sorbents have higher aromaticity and increased crystal graphitic layers. The biomass sorbents demonstrated rapid and efficient adsorption of p-nitrophenol, comparable to commercial activated carbon Norit GSX. Adsorption characteristics followed the Redlich-Peterson isotherm, Freundlich isotherm and pseudo-second-order kinetic model. p-nitrophenol adsorption onto the biomass sorbents followed multi-layer chemisorption and are primarily controlled by the electron donor-acceptor complexes mechanism, π-π interactions and steric effects. Boreal peat activated carbons are promising substitutions for traditional commercial activated carbons for water purification industries because of the low cost and abundance of precursors in North America, simple production route, and low energy consumption during the manufacture. By adopting a similar manufacturing strategy, we argue that new types of bio-sorbents can be obtained for treating organic molecules in wastewater.

Preparing boreal peat carbon sorbents for aqueous p-nitrophenol adsorption: Equilibrium and kinetic studies

ACS Fall 2020 Virtual Meeting

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