Enhanced removal of sulfonamide antibiotics from water by phosphogypsum modified biochar composite

The treatment of phosphogypsum leachate is more urgent than phosphogypsum

Phosphogypsum(PG) is one of the typical bulk industrial solid wastes generated in the phosphate chemical industry. Due to its huge production volume and immature resource treatment technology, a large amount of PG can only be stored and disposed in slag yards, and its impact on the ecological environment is becoming increasingly significant during long-term storage. Up to now, many researchers have focused their research on PG, with less attention paid to the PG leachate(PG-L). On the basis of the resource utilization of PG, this article analyzed the migration and transformation of pollutants and their impact on the ecological environment during long-term storage of PG. The content of pollutants in PG-L and PG was compared, and it was found that the content of toxic and harmful substances in PG-L was significantly higher than that in PG itself, and the pollution diffusion ability was greater than that of PG, the pollution of PG to the ecological environment is mainly caused by PG-L, indicating that the harmless treatment of PG-L is more urgent than PG. On the basis of traditional leachate treatment methods, a new technology of valuable element recovery and electrochemical synergistic treatment is proposed to achieve high value-added treatment of PG-L.

Insights into the enhanced adsorption of glyphosate by dissolved organic matter in farmland Mollisol: effects and mechanisms of action

Dissolved organic matter (DOM) is easy to combine with residual pesticides and affect their morphology and environmental behavior. Given that the binding mechanism between DOM and the typical herbicide glyphosate in soil is not yet clear, this study used adsorption experiments, multispectral techniques, density functional theory, and pot experiments to reveal the interaction mechanism between DOM and glyphosate on Mollisol in farmland and their impact on the environment. The results show that the adsorption of glyphosate by Mollisol is a multilayer heterogeneous chemical adsorption process. After adding DOM, due to the early formation of DOM and glyphosate complex, the adsorption process gradually became dominated by single-layer chemical adsorption, and the adsorption capacity increased by 1.06 times. Glyphosate can quench the endogenous fluorescence of humic substances through a static quenching process dominated by hydrogen bonds and van der Waals forces, and instead enhance the fluorescence intensity of protein substances by affecting the molecular environment of protein molecules. The binding of glyphosate to protein is earlier, of which affinity stronger than that of humic acid. In this process, two main functional groups (C-O in aromatic groups and C-O in alcohols, ethers and esters) exist at the binding sites of glyphosate and DOM. Moreover, the complexation of DOM and glyphosate can effectively alleviate the negative impact of glyphosate on the soil. This study has certain theoretical guidance significance for understanding the environmental behavior of glyphosate and improving the sustainable utilization of Mollisol.

Treating waste with waste: adsorption behavior and mechanism of phosphate in water by modified phosphogypsum biochar

The use of green methods to treat industrial waste and waste reuse has become a key environmental issue. In order to achieve this goal, this study treated waste phosphogypsum (PG) and produced modified PG biochar to adsorb and remove phosphorus from PG leachate, so that the PG pollution problem was controlled. In this study, PG was modified with sodium carbonate (Na2CO3) to prepare a modified PG biochar that was used for the removal of phosphorus-containing wastewater. An X-ray diffraction (XRD) analysis of the modified PG revealed that the main component was calcium carbonate (CaCO3), and a suitable amount of modified PG could load calcium oxide (CaO) onto the biochar and improve its physical properties. The experimental results showed that the modified PG biochar had a maximum phosphorus adsorption capacity of 132 mg/g. A further investigation of the mechanism of adsorption revealed the importance of electrostatic attraction and chemical precipitation, and it was found that the CaO in the modified PG biochar could effectively facilitate the conversion of phosphate to hydroxylapatite (Ca5(PO4)3OH) in water. The phosphorus removal rate from leachate obtained from a landfill containing PG was 99.38% for a specific dose of the modified PG biochar. In this study, a PG pollution control technology was developed to realize the goal of replacing waste with waste.

A review on carbon-based biowaste and organic polymer materials for sustainable treatment of sulfonamides from pharmaceutical wastewater

Frequent detection of sulfonamides (SAs) pharmaceuticals in wastewater has necessitated the discovery of suitable technology for their sustainable remediation. Adsorption has been widely investigated due to its effectiveness, simplicity, and availability of various adsorbent materials from natural and artificial sources. This review highlighted the potentials of carbon-based adsorbents derived from agricultural wastes such as lignocellulose, biochar, activated carbon, carbon nanotubes graphene materials as well as organic polymers such as chitosan, molecularly imprinted polymers, metal, and covalent frameworks for SAs removal from wastewater. The promising features of these materials including higher porosity, rich carbon-content, robustness, good stability as well as ease of modification have been emphasized. Thus, the materials have demonstrated excellent performance towards the SAs removal, attributed to their porous nature that provided sufficient active sites for the adsorption of SAs molecules. The modification of physico-chemical features of the materials have been discussed as efficient means for enhancing their adsorption and reusable performance. The article also proposed various interactive mechanisms for the SAs adsorption. Lastly, the prospects and challenges have been highlighted to expand the knowledge gap on the application of the materials for the sustainable removal of the SAs.

The effect of the ageing process on the desorption of nonylphenol in black carbon-sediment systems: a kineto-mechanistic and modeling investigation

Black carbon (BC) exhibits promising potential as a sediment amendment owing to its commendable adsorption capacity for hydrophobic organic contaminants (HOCs), thereby resulting in HOC-laden sediments. Desorption kinetic studies play a crucial role in comprehending the release potential of HOCs from BC-sediment systems. Although the adsorption capacity of BC for HOCs has been found to decrease with aging, there is limited research on its impact on HOC desorption kinetics. In this study, BCs derived from agricultural waste (rice straw carbon, RC) and industrial waste (fly ash carbon, FC), respectively, were used to investigate the desorption kinetics of nonylphenol (NP). Additionally, a predictive model was established using the fitting parameters obtained from the modified two-domain model. The results showed that desorption of NP was divided into three fractions: rapid fraction (Frap), slow fraction (Fslow) and resistant fraction (Fr). BCs significantly decreased, while ageing increased the desorption amount and rate of NP. The performance of RC in controlling NP release was superior to that of FC. The predicted values calculated by the established model exhibit significant positive correlations with the measured values (p < 0.01). Additionally, the correlation analysis between sorption sites and desorption fractions revealed that the concentration of NP in the desorbing fraction was nearly equivalent to that of NP in partition sites within aged sediment/FC-sediment systems. However, the aged RC-sediment systems do not conform well to this rule. In other words, the estimation of NP release risk from sediments with a strong adsorbent would be overestimated, if Frap + Fsolw is considered equivalent to the desorbing fraction.

Biochar as Alternative Material for Heavy Metal Adsorption from Groundwaters: Lab-Scale (Column) Experiment Review

The purpose of this manuscript is to present a review of laboratory experiments (including methodology and results) that use biochar, a specific carbon obtained by a pyrolysis process from different feedstocks, as an alternative material for heavy metal adsorption from groundwater. In recent years, many studies have been conducted regarding the application of innovative materials to water decontamination to develop a more sustainable approach to remediation processes. The use of biochar for groundwater remediation has particularly attracted the interest of researchers because it permits the reuse of materials that would be otherwise disposed of, in accordance with circular economy, and reduces the generation of greenhouse gases if compared to the use of virgin materials. A review of the different approaches and results reported in the current literature could be useful because when applying remediation technologies at the field scale, a preliminary phase in which the suitability of the adsorbent is evaluated at the lab scale is often necessary. This paper is therefore organised with a short description of the involved metals and of the biochar production and composition. A comprehensive analysis of the current knowledge related to the use of biochar in groundwater remediation at the laboratory scale to obtain the characteristic parameters of the process that are necessary for the upscaling of the technology at the field scale is also presented. An overview of the results achieved using different experimental conditions, such as the chemical properties and dosage of biochar as well as heavy metal concentrations with their different values of pH, is reported. At the end, numerical studies useful for the interpretation of the experiment results are introduced.

Phosphogypsum-Modified Vinasse Shell Biochar as a Novel Low-Cost Material for High-Efficiency Fluoride Removal

In this study, vinasse shell biochar (VS) was easily modified with phosphogypsum to produce a low-cost and novel adsorbent (MVS) with excellent fluoride adsorption performance. The physicochemical features of the fabricated materials were studied in detail using SEM, EDS, BET, XRD, FTIR, and XPS techniques. The adsorption experiments demonstrated that the adsorption capacity of fluoride by MVS was greatly enhanced compared with VS, and the adsorption capacity increased with the pyrolysis temperature, dosage, and contact time. In comparison to chloride and nitrate ions, sulfate ions significantly affected adsorption capacity. The fluoride adsorption capacity increased first and then decreased with increasing pH in the range of 3-12. The fluoride adsorption could be perfectly fitted to the pseudo-second-order model. Adsorption isotherms matched Freundlich and Sips isotherm models well, giving 290.9 mg/g as the maximum adsorption capacity. Additionally, a thermodynamic analysis was indicative of spontaneous and endothermic processes. Based on characterization and experiment results, the plausible mechanism of fluoride adsorption onto MVS was proposed, mainly including electrostatic interactions, ion exchange, precipitation, and hydrogen bonds. This study showed that MVS could be used for the highly efficient removal of fluoride and was compatible with practical applications.

Comparative Study of the Removal Efficiency of Nalidixic Acid by Poly[(4-vinylbenzyl)trimethylammonium Chloride] and N-Alkylated Chitosan through the Ultrafiltration Technique and Its Approximation through Theoretical Calculations

Emerging antibiotic contaminants in water is a global problem because bacterial strains resistant to these antibiotics arise, risking human health. This study describes the use of poly[(4-vinylbenzyl) trimethylammonium chloride] and N-alkylated chitosan, two cationic polymers with different natures and structures to remove nalidixic acid. Both contain ammonium salt as a functional group. One of them is a synthetic polymer, and the other is a modified artificial polymer. The removal of the antibiotic was investigated under various experimental conditions (pH, ionic strength, and antibiotic concentration) using the technique of liquid-phase polymer-based retention (LPR). In addition, a stochastic algorithm provided by Fukui's functions is used. It was shown that alkylated N-chitosan presents 65.0% removal at pH 7, while poly[(4-vinylbenzyl)trimethylammonium chloride] removes 75.0% at pH 9. The interaction mechanisms that predominate the removal processes are electrostatic interactions, π-π interactions, and hydrogen bonding. The polymers reached maximum retention capacities of 1605 mg g-1 for poly[(4-vinylbenzyl) trimethylammonium chloride] and 561 mg g-1 of antibiotic per gram for alkylated poly(N-chitosan). In conclusion, the presence of aromatic groups improves the capacity and polymer-antibiotic interactions.