Ball-milled biochar for galaxolide removal: Sorption performance and governing mechanisms

Qianru Zhang; Jianmei Wang; Honghong Lyu; Qing Zhao; Lisi Jiang; Li Liu

doi:10.1016/j.scitotenv.2019.01.005

Ball-milled biochar for galaxolide removal: Sorption performance and governing mechanisms

Sci Total Environ. 2019 Apr 1:659:1537-1545. doi: 10.1016/j.scitotenv.2019.01.005. Epub 2019 Jan 3.

Authors

Qianru Zhang¹, Jianmei Wang², Honghong Lyu³, Qing Zhao⁴, Lisi Jiang², Li Liu⁴

Affiliations

¹ Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China. Electronic address: zhangqianru@iae.ac.cn.
² Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; University of Chinese Academy of Sciences, Beijing 100049, China.
³ Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China; School of Energy and Environmental Engineering, Hebei University of Technology, Tianjin 300401, China.
⁴ Key Laboratory of Pollution Ecology and Environmental Engineering, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, China.

PMID: 31096363
DOI: 10.1016/j.scitotenv.2019.01.005

Abstract

The environmental risk of galaxolide (HHCB) spurs the need to develop efficient and economical removal technology. Although sorption is one of the best removal approaches, studies on sorption of HHCB by biochar were limited. With the purpose of combining the advantages of ball-milling and sorption technologies, six ball-milled biochars (BM-biochars) varied with biomasses and pyrolysis temperature were produced, characterized, and tested for HHCB removal from aqueous solution. At an initial HHCB concentration of 2 mg L^-1, the unmilled and BM-biochars adsorbed 330-746 and 609-2098 mg kg^-1 of HHCB, respectively. The increase in sorption capacities (about 3-fold increase) was mainly ascribed to the increase in BM-biochar's external and internal surface area, pore volume and pore size, and the exposure of the graphitic structure. The removal of HHCB by the BM-biochars increased with increasing pyrolysis temperature. For lower temperature biochar (300 °C wheat straw biochar, WS300), hydrophobic partitioning played a major role in HHCB sorption onto unmilled biochar (log K_oc/log K_ow value of WS300 was 0.772 at a C_e of 1 mg L^-1). Ball milling reduced the hydrophobicity of 300 °C biochar, which diminished the HHCB sorption. However, increased surface area, pore volume, pore size, and graphitic structure provided additional sorption sites, resulting in enhanced HHCB uptake (log K_oc/log K_ow value of BMWS300 was 1.23 at a C_e of 1 mg L^-1). For higher temperature biochars (500 and 700 °C), ball milling mainly enhanced HHCB sorption onto high temperature biochars via surface adsorption, π-π interaction, and pore filling. For WS500, 77.9% of HHCB removal was due to surface adsorption. Ball milling increased this percentage to 96.7% for BMWS500. This work highlighted the potential of ball milling as an excellent engineering method to improve biochar's sorption properties.

Keywords: Ball mill; Biochar; Galaxolide; Sorption.

MeSH terms

Benzopyrans / analysis
Benzopyrans / chemistry*
Charcoal
Models, Chemical
Water Pollutants, Chemical / analysis
Water Pollutants, Chemical / chemistry*
Water Purification / methods*

Substances

Benzopyrans
Water Pollutants, Chemical
biochar
galaxolide
Charcoal