The production of hydroxyl radicals (·OH) via reduced humin oxygenation is well established. As biochar is widely used in environmental restoration, its coexistence with humin in restored soils may affect ·OH generation due to its electron transfer ability. However, the role of biochar in ·OH generation by humin remains largely unexplored. Herein, we investigated the ·OH generation by humin-biochar at different mass ratios. Our results indicated that biochar could significantly enhance the ·OH production by humin when the mass of humin exceeded that of biochar. Notably, when the mass ratio of humin to biochar was 50, the ·OH produced reached 75.1 μM, which is nearly 1.7 times the amount generated by humin alone (43.1 μM). Both single-electron and two-electron transfer pathways coexisted in ·OH generation by humin-biochar. C = O in humin were necessary conditions for the production of ·OH, while the presence of C = C in biochar promoted the generation of ·OH. Using graphene and carbon nanotubes both rich in C = C groups as the model compounds, humin-graphene and humin-carbon nanotubes produced ·OH at 122 μM and 98.8 μM, respectively, significantly higher than those generated by humin alone (43.1 μM). This result confirmed the promoting effect of aromatic C = C on ·OH generation. By contrast, when the biochar mass was greater than or equal to that of humin, ·OH generation was inhibited due to the significant reduction of C = O. In this case, environmentally persistent free radicals (EPFRs) in biochar were the primary structures responsible for ·OH production. This study provides comprehensive insights for the first time into the influence of biochar on ·OH generation by humin and offers a new potential method for the green and efficient removal of pollutants.
Shangqi Ge,Wenhao Jiang,Lingwei Zheng,Xinyu Xie,Yize Pan
High concentrations of lead in soil will greatly weaken the stabilization/solidification effect. Humin (HM) is expected to improve this process because it is a neutral, insoluble, porous and green material as well as an eco-friendly adsorbent extracted from natural peat soil . However, HM has not been studied with respect to the stabilization/solidification (S/S) characteristics of potentially toxic element (PTE)-contaminated soil due to its different extraction sources and methods, as well as complex properties. To study these effects, insoluble HM was extracted for treatment of high-lead contaminated soil by cement-based S/S. The experimental results show that HM has a strong adsorption capacity for lead with a maximum adsorption capacity of 200.2 mg kg −1 . The negative influence of a high content of lead on the compressive strength over a 0–90-day period is weakened after adding HM to the soil, wherein a competitive mechanism between HM and a high concentration of lead is proposed. The lead leaching concentration of stabilized soil is significantly decreased under different leaching methods from 0 to 60 days and then decreases slowly. The lead speciation results for the stabilized soil determined through the Tessier sequential extraction method show that HM promotes the gradual chemical transformation of lead from exchangeable and carbonate-bound fractions to a more stable state, with respective decreases of 27.5% and 15.1%. In addition, SEM-EDS images show that HM with a high porosity and specific surface area coexists well with cement, which promotes the stabilization of lead. In conclusion, HM contributes to decreasing the mobility and bioavailability of lead and achieving environmental remediation.
Tartaric acid (TA) is an important component of plant rhizosphere secretion, having a certain influence on the adsorption and desorption behavior of heavy metals in soil. Humin could serve as an environmentally compatible passivator of heavy metal in soil. The aims of this study were to simulate the adsorption of Pb (II) via humin in a soil solution, explore the effects of TA on the adsorption of Pb (II) by humin and elucidate the mechanism of its influence. The results indicated that the adsorption of Pb (II) on the surface of humin within and without TA was consistent with the Langmuir isotherm equation and the pseudo-secondary kinetic model (R 2 > 0.99). The effect of TA on adsorption was related to the concentration of TA. With the increasing of TA concentration, the adsorption of Pb (II) by humin showed a peak change and the adsorption amount reached the maximum with 0.5 mmol L −1 humin, is 192.31 mg L −1 with 0.1 mmol TA. Basing on adsorption experiments and characterization of FTIR, SEM, EDX and XPS. It revealed that the oxygenated groups of TA can be combined with humin by hydrogen bonding, in the low concentration TA (less than 0.5 mmol L −1 ), which is equivalent to an increment of the carboxyl group on the surface of humin, thus adsorption amount was increased. The increasing of the concentration of TA led to an increment of free TA in the solution, which would complex with the lead ions in the solution, and indirectly reduce the amount of Pb(II) adsorption on the humin.
危险品化学品经营许可证（带存储）