Effects of UV Light Treatment on Functional Group and Its Adsorption Capacity of Biochar

Abstract

This study aimed to investigate the impact of UV treatment on the surface functionality and adsorption capacity of biochar, with the goal of enhancing its effectiveness as an adsorbent for toluene. The surface and near-surface functionality and structure of biochar were studied to evaluate the impact of UV treatment by utilizing X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and Brunauer–Emmett–Teller (BET) techniques. Biochar was generated by pyrolyzing wood chips at 900 °C without any oxidant injection in order to increase their carbon content. To boost biochar’s adsorption capability, UV irradiation on the biochar is utilized before and during the penetration process. Toluene was selected as the target absorbing material. The equilibrium adsorption capacity and rate were simulated using the Wheeler equation. It was found that the adsorption capacity of biochar increased significantly after pretreatment with ultraviolet light irradiation with a wavelength of 254 nm and an intensity of 280 μW/cm2 and reached a saturated state after 15 h. SEM and XPS showed that the UV-biochar modification technology not only improved the pore structure of biochar, but also increased the content of -O-containing functional groups on the surface of biochar and improved the adsorption capacity of biochar. The experimental results for sample M50_Uu demonstrated significant improvement in adsorption performance. The adsorption saturation time increased by 80%, and the equilibrium adsorption capacity rose from 12.80 mg/g to 54.60 mg/g. The main reason for the adsorption capacity increase by UV treatment is functional group formation, of which rate linearly increases with pretreatment energy until 11 W·hr/gbiochar, after which the increase rate is slow.

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

“…As the pH increases to a range of 7.7–9.7, TC is predominantly present as TC – . Finally, when the pH exceeds 9.7, the majority of TC exists as TC. − As shown in the inset of Figure b, the surface of PMABC-200 was negatively charged when the pH value was between 3 and 11. Therefore, when the pH values were 3, 5, and 7, PMABC-200 demonstrated remarkable TC adsorption efficacy owing to the attenuated electrostatic repulsion between negatively charged PMABC-200 and neutral TC (pH 5 and 7) and TC + (pH = 3).…”

“… 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.…”

“…It is widely used for adsorbing pollutants during wastewater treatment. − The properties of BC have an important effect on its adsorption capacity and are mainly determined by pyrolysis factors such as pyrolysis temperature, feedstock material dosage, and heat-insulation time. 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 .…”