Adsorptive Removal of Trichloroethylene in Water by Crop Residue Biochars Pyrolyzed at Contrasting Temperatures: Continuous Fixed-Bed Experiments

Ming Zhang,Yong Sik Ok,Mahtab Ahmad,Meththika Vithanage,Mohammad I Al-Wabel,Anushka Upamali Rajapaksha,Hyuck Soo Kim,Sang Soo Lee

doi:10.1155/2015/647072

Abstract

Biochar (BC) has attracted great attention as an alternative sorbent to activated carbon (AC). Objective of this study was to determine trichloroethylene (TCE) removal by soybean stover BC pyrolyzed at 300 (BC300) and 700°C (BC700) in continuous fixed-bed column. Columns packed with BC300, BC700, and AC reached breakthrough time in 1.1, 27.0, and 50.7 h, respectively. BC700 had higher TCE adsorption capacity than BC300 due to its higher surface area, nonpolarity, and aromaticity. The sorption capacities of AC (774.0 mg g−1) and BC700 (515.1 mg g−1) were 21.6 and 14.4 times higher than that of BC300 (35.9 mg g−1). The lower desorption rate of TCE from BC300 than BC700 and AC may be attributed to the strong binding/partition of TCE to the noncarbonized part of BC. Thomas model also adequately described the adsorption data indicating interphase mass transfer. Overall, AC showed best efficiency for removing TCE from water in column experiments. However, although sorption and desorption capabilities of BC700 were a little lower than AC, it is still a good alternative for AC to remove organic contaminants such as TCE from water due to its cost-effectiveness.

Highlights

Char, a solid material produced from carbonaceous biomass, is emerging as an alternative to activated carbon (AC) with lower cost and environmental advantages
The lower desorption rate of TCE from BC pyrolyzed at 300 (BC300) than BC700 and AC may be attributed to the strong binding/partition of TCE to the noncarbonized part of BC
The BCs were denoted as BC300 and BC700 based on pyrolysis temperature

Summary

Introduction

A solid material produced from carbonaceous biomass, is emerging as an alternative to activated carbon (AC) with lower cost and environmental advantages. Biochar means black carbon derived from biomass pyrolysis and closely resembles activated carbon with a structured carbon matrix and a medium-to-high surface area. Biochar has a wide range of chemical compositions and surface properties depending on biomass type and pyrolysis temperature [7]. Several studies have already reported the effect of pyrolysis temperature on sorption properties of biochars [8, 9]. Higher temperature-pyrolyzed-biochar possesses high surface area, carbon content, aromaticity, and hydrophobicity, which lead to the increase of sorption capacity towards contaminants, especially for the nonionized chemicals [10]. Lower temperature-pyrolyzed-biochar was believed to be effective for polar organics and heavy metals due to abundant polar groups on biochar surface [10].

Objectives

Methods

Results

Conclusion