Mechanism Of Humic Acid Research Articles

Insight into the Mechanism of Humic Acid’s Dissolution Capacity for Lignin in the Biomass Substrates

The poor solubility of lignin in most solvents causes the biggest challenges in lignin valorization to improve overall biorefinery economics. In this work, humic acid (HA), a natural surfactant, was investigated with respect to its ability to assist in biomass delignification. After obtaining a baseline level of delignification using standard HA, a mechanism of action was proposed in which the lignin removal was driven by hydrophobic interactions. To explore this hypothesis, HA was modified in two ways. One batch was sulfonated to increase HA hydrophilicity, while the other was esterified to increase HA hydrophobicity. Treatment of the same substrates with the modified HA materials revealed that elevated hydrophobicity provided a further increase in the level of delignification. It was found that the solubility of lignin in the HA solution was increased with the enhancement of HA hydrophobicity from 12.2% (S-HA) to 16.8% (E-HA). Therefore, the initial hypothesis was confirmed that HA-derived delignification improvements appear to be a function of hydrophobic interactions. These results should aid further investigation into choosing surfactants (ideally those that are biobased) for utility in biorefinery processes.

New insights into the adsorption behavior of thiacloprid at the microfibers/water interface: Role of humic acid

Dissolved organic matter regulates the interaction between microplastics (MPs) and organic pollutants. Here, this paper investigated the effect and mechanism of humic acid (HA) on the adsorption behavior of thiacloprid at two microfibers (MFs)/water interface, and compared the differences in the performance of MFs and pure MPs. The results showed that 10 mg L−1 HA decreased the adsorption capacity and the partition coefficient KD of thiacloprid on MFs and pure MPs. Spectral analysis showed that HA could form hydrogen bonds and van der Waals forces with both MPs and thiacloprid, ultimately affecting the adsorption behavior of thiacloprid at MPs/water interface via competitive adsorption and bridging effect. Furthermore, two-dimensional correlation spectroscopy demonstrated that thiacloprid was preferentially adsorbed onto MPs compared with HA. Finally, density functional theory calculation demonstrated that phenolic-OH, –COOH, and alcoholic-OH played critical roles in competing adsorption and bridging effect. This study offers a theoretical foundation for a better comprehension of the adsorption behavior of organic pollutants at the MPs/water interface.

Inhibition of humic acid on copper pollution caused by chalcopyrite biooxidation

Humic acid has the advantages of wide source, easy availability and environmental friendliness, which may be a good choice for inhibiting chalcopyrite biooxidation and alleviating copper pollution. However, there are few researches on the inhibitory effect and mechanism of humic acid on the biooxidation of chalcopyrite. In order to fill this knowledge gap, this study proposed and validated a novel method for inhibiting chalcopyrite biooxidation by means of humic acid. The results showed that the biooxidation of chalcopyrite could be effectively inhibited by humic acid, which consequently decreased the release of copper ions. Humic acid with a concentration of 120 ppm had the best inhibitory effect, which reduced the biooxidation efficiency of chalcopyrite from 40.7 ± 0.5 % to 29.3 ± 0.8 %. This in turn suggested that humic acid could effectively suppress the pollution of copper under these conditions. The analysis results of solution parameters, mineral surface morphology, mineral phases and element composition showed that humic acid inhibited the growth of Acidithiobacillus ferrooxidans, promoted the formation of jarosite and intensified the passivation of chalcopyrite, which effectively hindered the biooxidation of chalcopyrite, and would help to alleviate the pollution of copper.

腐殖酸对硫酸盐还原菌厌氧还原硫酸盐的抑制效果及其机理研究

腐殖酸对硫酸盐还原菌厌氧还原硫酸盐的抑制效果及其机理研究

Removal of Humic Acid from Water by Magnetic Chitosan-Grafted Polyacrylamide

For high-efficiency removal of humic acid (HA), a natural organic matter in the water source, an adsorbent named magnetically modified chitosan-grafted polyacrylamide (MC-g-PAM) was developed by using an in situ coprecipitation method. Analytical instruments, such as a Fourier transform infrared (FTIR) spectroscope, scanning electron microscope (SEM), vibrating sample magnetometer (VSM), and specific surface area tester (BET), were used to characterize and analyze this material. With the aid of batch tests, the removal efficiency and mechanism of humic acid in water samples were investigated. The results show that the specific surface area and specific saturation magnetization values of the prepared MC-g-PAM are 27.065 m2·g-1 and 9.63 emu·g-1, respectively. The adsorption of humic acid by MC-g-PAM is an endothermic process and the Langmuir isotherm model and the pseudo-second-order kinetic equation fit the adsorption process well. At 25℃, the equilibrium adsorption capacity of MC-g-PAM to humic acid reaches 120.77 mg·g-1.

Identification Influence Mechanism of Humic Acid in the Degradation of Decabromodiphenyl Ether by the BC@Ni/Fe Nanoparticles

Identification Influence Mechanism of Humic Acid in the Degradation of Decabromodiphenyl Ether by the BC@Ni/Fe Nanoparticles

Adsorption Behavior and Mechanism of Humic Acid on Aminated Magnetic Nanoadsorbent

Adsorptive removal of aqueous humic acid (HA) with aminopropyl functionalized silica coated Fe3O4 nanoparticles was investigated. The adsorption isotherm of HA can be described very well by both the Langmuir and Freundlich models and the theoretical maximum adsorption capacity was 181.82 mg/g. Adsorption kinetics followed both the diffusion-controlled and the attachment-controlled process. HA adsorption increased monotonously with increasing solution pH. The presence of cations in solution, results in augmented HA adsorption. The adsorbent exhibits excellent desorption and regeneration properties. Zeta potential and XPS analysis reveal that electrostatic interaction and surface complexation between protonated amino groups and the disassociated HA molecules are the main adsorption mechanism.

Adsorption Mechanism of Humic Acid on Cu/Fe Bimetallic Particles and Its Influence on the Reduction of Nitrobenzene in Groundwater

Humic acid (HA) is ubiquitous in groundwater, and poses great influence on the biogeochemical controls on, as well as treatment of, contaminants. This study deals with the adsorption of HA on a bimetallic iron system, Cu/Fe, and its influence on the reduction of nitrobenzene in synthetic groundwater. The adsorption kinetics, isotherms, and enthalpy of HA on bimetallic Cu/Fe particles are investigated. Compared with the adsorption of HA on Fe0 particles, the adsorption on Cu/Fe is faster than that on Fe0. The adsorption isotherms of HA at different pH values and temperatures show that the adsorption is always greater on Cu/Fe than on Fe0, and increases when the pH decreases and temperature increases. Moreover, the influences of pH and temperature on adsorption by Cu/Fe are less than those observed in adsorption on Fe0. The adsorption enthalpy on Cu/Fe is lower than that on Fe0, and both adsorptions are spontaneous and endothermic. Characterization of the corrosion products by SEM-EDX, XRD, and XPS reveals the appearance of maghemite (γ-Fe2O3) and magnetite (Fe3O4) on Cu/Fe with HA adsorption, which were more crystalline than those of Fe0, indicating that bimetallic Cu/Fe facilitated the formation of crystalline corrosion products. The adsorption of HA accelerates the release of iron ions but suppresses the reduction of nitrobenzene. Compared with Fe0, Cu/Fe accelerates the adsorption of HA and Cu/Fe increases the reduction of nitrobenzene. The suppression on nitrobenzene reduction increased with the increase in HA concentration.

Adsorption Mechanism of Humic Acid on Attapulgite Based on Stumm-Schindle Surface Complexation Model

Attapulgite from Xuyi in Jiangsu was characterized by X-ray spectrometer and FT-IR spectrophotometer, the coordination reaction degree of attapulgite/water interface and adsorption mechanism of humic acid(HA) on attapulgite was analyzed by Stumm-Schindle(SS) surface complexation model. The results showed that the main component of attapulgite is magnesia-alumina acid salt, the surface charge on attapulgite adapted from hydrolysates of Si-O and Al-O broken bond. After adsorption, zeta potential decreased firstly and then increased with ionic strength increasing, reduced with a pH value increasing. The zero point charge (pHzpc) of attapulgite was about 4~5, zeta potential and adsorption capacity reached the maximum values when pH= 4 and the minimum values when pH=12. The adsorption capacity increased with ionic strength rising. SS surface complexation model could well explain attapulgite / water interfacal coordination reaction, ionic strength can promote the interfacial coordination reaction and reduce electrostatic repulsion effects on adsorption, which has a definite theoretical and practical significance for guiding adsorption experiment and application of attapulgite in water-treatment technology.

Effects and mechanism of humic acid on chromium(VI) removal by zero-valent iron (Fe 0) nanoparticles

The present study dealt with the performance evaluation of the nanoscale Fe 0 systems for the remediation of chromium contaminated groundwater in the ambient environment. The role of humic acid (HA) in the Cr(VI) removal and the reduction mechanism were investigated. HA was found to exert an obvious inhibitory effect on Cr(VI) removal by Fe 0 nanoparticles, and the Cr(VI) removal efficiencies decreased from 71.6%, 58.4%, 57.8% to 38.5% with the increasing HA concentrations (0, 5, 10, 20 to 40 mg L −1). A dual effect of humic acid on chromium(VI) reduction by Fe 0 nanoparticles was observed. HA adsorbed on the surface of Fe 0 nanoparticles and occupied the active surface sites, leading to the decrease in Cr(VI) reduction rates. Greater was the adsorbed HA, the more obvious was the inhibitory effect. However, the HA adsorption on iron surface areas was one of the factors leading to the decreased reduction rate. The appropriate starch dosage (0.5 g per 0.3 g nanoscale Fe 0 particles) could definitely eliminate the inhibitory effect of humic acid.