Abstract
Biochar adsorption presents a potential remediation method for the control of hydrophobic organic compounds (HOCs) pollution in the environment. It has been found that HOCs bound on biochar become less bioavailable, so speculations have been proposed that HOCs will persist for longer half-life periods in biochar-amended soil/sediment. To investigate how biochar application affects coupled adsorption-biodegradation, nonylphenol was selected as the target contaminant, and biochar derived from rice straw was applied as the adsorbent. The results showed that there was an optimal dosage of biochar in the presence of both adsorption and biodegradation for a given nonylphenol concentration, thus allowing the transformation of nonylphenol to be optimized. Approximately 47.6% of the nonylphenol was biodegraded in two days when 0.005 g biochar was added to 50 mg/L of nonylphenol, which was 125% higher than the relative quantity biodegraded without biochar, though the resistant desorption component of nonylphenol reached 87.1%. All adsorptive forms of nonylphenol (f rap, f slow, f r) decreased gradually during the biodegradation experiment, and the resistant desorption fraction of nonylphenol (f r) on biochar could also be biodegraded. It was concluded that an appropriate amount of biochar could stimulate biodegradation, not only illustrating that the dosage of biochar had an enormous influence on the half-life periods of HOCs but also alleviating concerns that enhanced HOCs binding by biochar may cause secondary pollution in biochar-modified environment.
Highlights
Compared with conventional carbonaceous materials such as commercial activated carbon, the primary advantages of biochar are its low cost and the diversity of biomass from which it can be produced [1]
Nonylphenol was selected as a target contaminant and rice-straw biochar as an adsorbent to investigate the effects and mechanism of biochar dosage on nonylphenol biodegradation
The results showed that the optimal biochar dosage varied depending on the concentration of nonylphenol
Summary
Compared with conventional carbonaceous materials such as commercial activated carbon, the primary advantages of biochar are its low cost and the diversity of biomass from which it can be produced [1]. Because of its strong adsorption capacity, biochar has attracted increasing interest in recent years for the immobilization of HOCs [2,3,4] and is a promising solution in remediation [5,6]. It was proposed that biochar application suppressed the transformation of HOCs, resulting in a longer half-life and persistence in the soil and/or sediment. Muter et al investigated the influence of biochar on the persistence of the herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) in soils and found that after 37 days, the biodegradation rate was significantly reduced when 5.3% biochar was applied, dropping from 100% to 69.3% (P < 0.01) [17]. A similar phenomenon was observed by Xin et al, who found that the transformation rate of 2,2’,4,4’-tetrabromodiphenyl ether was decreased by 87.50–92.19% when 1% biochar was added to the soil [18]
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