Abstract
In this paper, biochar (BC) was prepared from discarded grapefruit peel and modified to prepare magnetic biochar (MBC). Physical and chemical properties of BC and MBC were characterized, and the results showed that the type of iron oxide loaded by MBC was γ-Fe2O3. Compared with BC, MBC has a larger specific surface area and pore volume, with more oxygen-containing functional groups on the surface. BC and MBC were used to adsorb and remove endocrine-disrupting chemical (EDC) bisphenol A (BPA) from simulated wastewater. The results showed that the adsorption kinetics and adsorption isotherm of BPA adsorption by BC and MBC were mainly in accordance with the pseudo-second-order kinetics model and the Langmuir model. This indicates that the adsorption of BPA on BC and MBC is mainly a chemically controlled monolayer adsorption. Adsorption thermodynamics show that BC and MBC adsorption of BPA is a spontaneous exothermic reaction, and lowering the temperature is conducive to the adsorption reaction. The effect of solution pH on the adsorption of BPA by both was significant. The optimum pH for BC and MBC to absorb BPA was 6 and 3, respectively. The concentration of Na+ in the range of 0–0.10 mol·L−1 can promote the adsorption of BPA to MBC. MBC loaded with γ-Fe2O3 not only has excellent magnetic separation ability, but can also reach about 80% of the initial adsorption capacity after four cycles of adsorption. By analyzing the adsorption mechanism, it was found that the H-bond and the π–π electron donor–acceptor interaction (EDA) were the main forces for BC and MBC to adsorb BPA.
Highlights
Bisphenol A (BPA) is an emerging contaminant that is often detected in natural waters at levels of ng·L−1 or ug·L−1, making it a trace organic contaminant
The increase of the specific surface area is beneficial to the adsorption capacity of the adsorbent
The pore volume and aperture of magnetic biochar (MBC) are larger than that of BC, which is more conducive to the adsorption of macromolecules
Summary
Bisphenol A (BPA) is an emerging contaminant that is often detected in natural waters at levels of ng·L−1 or ug·L−1 , making it a trace organic contaminant. Res. Public Health 2020, 17, 1075 bisphenol A has been listed as a priority pollutant in water treatment in more and more countries and regions [7]. Bisphenol A in the environment can be released into the water body through the polycarbonate plastic’s natural degradation [8]. As a water treatment process, adsorption has the characteristics of a good effect, an easy operation, and low cost for bisphenol A [19,20]. There have been many studies on endocrine-disrupting chemicals (EDCs) of carbon-based materials, such as activated carbon [21,22,23], carbon black, carbon nanotubes [24,25], and biochar [26,27]. To solve the problem that biochar is difficult to recover after the adsorption of pollutants, some scholars proposed that biochar with magnetic properties can be prepared by chemical methods. The mechanism of adsorption of bisphenol A by biochar and magnetic biochar was discussed in combination with the characterization of the original biochar and magnetic biochar, so as to enrich the research of the adsorption of bisphenol A by biochar and magnetic biochar
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