The Effects of Chemical Oxidation and High-Temperature Reduction on Surface Functional Groups and the Adsorption Performance of Biochar for Sulfamethoxazole Adsorption

Abstract

Biochar is a beneficial adsorbent for the treatment of organic pollutants in the environment. The association of oxygen functional groups and adsorption behaviors has not been well investigated. In this paper, the oxidation-modified biochar (O-BC) and the reduction-modified biochar (R-BCX) were prepared by Co2+/peroxymonosulfate chemical oxidation and high-temperature reduction, respectively. The modified biochars were used to remove sulfamethoxazole (SMX) from water, and the adsorption amounts of biochar followed the order of R-BC700 (14.66 mg·L−1) > O-BC (4.91 mg·L−1) > BC (0.16 mg·L−1). Additionally, the effects of water chemical conditions (i.e., ionic strength, solution pH and humic acid (HA) concentration) on the adsorption of SMX on biochar, were further investigated. Combining physical adsorption, X-ray electron spectroscopy, and zeta potentiometer characterization techniques, the effect of functional groups on the adsorption mechanism was further explored, revealing the importance of various oxygen functional groups for SMX adsorption. The results showed that C=O and C=C, resulting in π–π interaction, were in favor of the adsorption of SMX, while C-O was not conducive to the adsorption of SMX, due to the steric hindrance and the negative surface charge. Additionally, the hydrophobic effect of the biochar was also one of the adsorption mechanisms.

O2-Involved Electro-activation of Persulfate on Oxidized Carbon Black for Effective Sulfamethoxazole Degradation: Key Role of Side-Reactive Oxygen Reduction

“…With the oxidation degree increase of OCB materials from air calcination, the electro-adsorptive proportion of SMX removal consequently rose from an initial 21.6% to 27.0% (CB300) and 52.9% (CB600, Figures B,C and S4B). The strongest electro-adsorption ability of CB600 could be ascribed to the most oxygen functional groups on its surface . Oxygen functional groups could serve as adsorbing sites via hydrogen bonding to remove SMX. , In addition, hydrophilic −OH and −COOH groups were conducive to the transportation of dissolved SMX to the OCB surface .…”

Enhanced Adsorptive Removal of Tetracycline by Phosphomolybdic Acid-Modified Low-Temperature Sludge Biochar

“… We conducted further peak fitting and calculation of the Mo 3d fine spectrum of PMABC-200. The characteristic peaks at 232.7 and 235.7 eV corresponded to MoO 3 , whereas those at 231.9 and 234.8 eV corresponded to MoO 4 . − As presented in Table S1, the content of oxygen-containing functional groups (such as C–OH, C–O–C, and CO) on the surface of PMABC-200 was higher than that of BC-200, with the exception of the O–CO group. The total content of the oxygen-containing groups on the surface of PMABC-200 (41.5%) was greater than that of BC-200 (39.4%), indicating that new oxygen-containing groups were generated on PMABC-200 through the modification with phosphomolybdic acid oxidation.…”

“…However, high pyrolysis temperatures still have some drawbacks, such as high energy consumption, low BC yield, 23 and few surface functional groups, 24 which are not conducive to pollutant removal. 25 In contrast, BC prepared by low-temperature pyrolysis can retain many surface oxygen-containing functional groups, which are beneficial for enhancing its adsorption performance. 26 many advantages, such as low energy consumption, little organic matter leaching, and less air pollutant generation from the feedstock material during sludge pyrolysis.…”

“…Among them, pyrolysis temperature (200–900 °C) is the most important factor affecting the adsorbability of generated BCs. − Notably, BC has generally been prepared at high temperatures (>400 °C) in many studies, as such BC possesses high specific surface area (SSA) and large pore volume (PV). However, high pyrolysis temperatures still have some drawbacks, such as high energy consumption, low BC yield, and few surface functional groups, which are not conducive to pollutant removal . In contrast, BC prepared by low-temperature pyrolysis can retain many surface oxygen-containing functional groups, which are beneficial for enhancing its adsorption performance .…”

Reviewing the effect of pyrolysis temperature on the fourier-transform infrared spectra of biochars

“…Biochar has also been considered as an environmentally friendly remediator in recent years (Ahmad et al, 2016;Abbas et al, 2018a;Abbas et al, 2018b (Hou et al, 2022). As mentioned, this work focused on how pyrolysis temperatures affect biochar surface properties and how the intensity of peaks corresponds to the functional groups in FTIR patterns.…”