Abstract
Here adsorption studies were proposed on a carboxylated sludge biochar (CSB) material modified by HNO3 to assess its capacity in the removal of cobalt from aqueous solution. The as-prepared sludge biochar material was characterized by Brunauer-Emmett-Teller (BET) analysis, Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), energy-dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The isotherm process could be well described by the Langmuir isotherm model. The adsorption kinetics indicated that cobalt adsorption followed a pseudo-second-order kinetics model. The mechanism between Co(II) and biochar involved electrostatic interaction, ion exchange, surface complexation and physical function. The adsorption capacity on CSB was as high as 72.27 mg·g-1, surpassing original sludge biochar (SB) as CSB had abundant oxygen-containing functional groups and many hydroxyls, plus the BET surface areas increased when SB was modified by HNO3, which stimulated adsorption effect. Therefore, this work shows that CSB could be used as an efficient adsorbent to remove Co(II) in wastewater.
Highlights
Inorganic pollutants such as heavy metals have caused serious environmental concerns due to their non-biodegradable properties and potential carcinogenicity (He et al 2016; Ma et al 2017)
The BET surface area of sludge biochar increased after treatment with HNO3
In the follow-up experiments, it was proved that carboxylated sludge biochar (CSB) has ascendant adsorption performance
Summary
Inorganic pollutants such as heavy metals have caused serious environmental concerns due to their non-biodegradable properties and potential carcinogenicity (He et al 2016; Ma et al 2017). Adsorbents have been explored extensively for wastewater purification by many researchers include carbonaceous, cellulose, and biochar (Hsu et al 2009; He et al 2016). Among those adsorbents, biochar has gained increasing recent favour due to its advantages as an adsorption material. The associated pore structure on the biochar is positively correlated to a large surface area for physical adsorption and its inherent functional groups, such as hydroxyl and carboxyl, could make chemical adsorption sites of heavy metal ions possible (Cougnaud et al 2005; Pawluk & Fronczyk 2015; Shanmuganathan et al 2017). The use of these types of waste materials would aid in reducing adsorption process cost and enhance their intrinsic value (Wu et al 2017; Cusack et al 2018)
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