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Magnetic porous adsorbent materials are widely favored for their large specific surface area, good adsorption performance, and ease of separation. This work provided a magnetic biochar derived from furfural residue (M-FRAC) with excellent adsorption properties for various pollutants, including Congo red (CR), Tetracycline (TC), Bisphenol A (BPA), and Cr6+. The influence of experimental parameters, such as pollutant concentration, contact time, and pH, on the adsorption properties of M-FRAC was studied in detail. The adsorption process was highly dependent on pH and initial contaminant concentration. All pollutant adsorption was favorable under acidic conditions. The optimal pH of the CR, TC, and Cr6+ adsorption was 5, 4, and 2, respectively, while that of BPA was in the range of 2–5. The experimental equilibrium adsorption amount of CR, TC, BPA, and Cr6+ by M-FRAC was 110.89, 602.81, 157.76, and 265.31 mg/g, respectively. The adsorption processes of pollutants on M-FRAC were in accordance with the Langmuir isotherm model. The adsorption kinetics fitted the pseudo-second-order (PSO) kinetics model. In addition, M-FRAC could be readily separated from solution by applying an external magnetic field. Therefore, the M-FRAC has a good application prospect in practical industrial wastewater treatment. [ABSTRACT FROM AUTHOR]

Lignosulfonates(LSs), by-products from chemical pulping processes, are low-value products with limited dispersion properties. The ability of commercially available horseradish peroxidase (HRP) to polymerize LS macromolecules and improve the dispersion properties of LSs was investigated. The polymerization of LSs proceeded efficiently under mild reaction conditions in an aqueous solution with HRP/H 2O 2. Gel permeation chromatography showed a significant increase in weight-average molecular weight ( Mw) of sulfonated kraft lignin and sodium lignosulfonate (NaLS) by 8.5-fold and 4.7-fold, respectively. The mechanism of polymerization was investigated by elemental analysis, surface charge measurement, headspace gas chromatography, infrared spectroscopy (IR), and hydrogen nuclear magnetic resonance spectrometry ( 1H-NMR). The functional group measurements indicated that HRP incubation did not reduce the sulfonic group content. However, it decreased the phenolic and methoxyl group contents. As the phenolic group content decreased, Mw increased as a power function. The polymerization was proposed to involve the random coupling of phenoxy radical intermediates. The radicals coupled with each other to form different inter-unit linkages, most of which were the β-O-4’ type, as the 1H-NMR spectra indicated. Moreover, the HRP/H 2O 2 incubation induced a significant improvement in the adsorption and dispersion properties of LSs. Therefore, the HRP/H 2O 2 incubation is a promising approach for industrial applications of LSs. [ABSTRACT FROM AUTHOR]

The direct preparation of adsorption materials from black liquor (BL) produced by the kraft pulping process has great potential in wastewater treatment. A three-dimensional nitrogen-doped porous carbon (N-BLSAC) with high specific surface area and large pore volume was synthesized. The adsorption performance of N-BLSAC for Cr(VI) and tetracycline (TC) was systematically investigated. Compared with the porous carbon prepared from purified lignin (N-PLAC), the adsorption performance of N-BLSAC for TC was more superior. It was not only attributed to the pore-filling effect but also the electrostatic interaction, hydrogen bonding, and π-π electron-donor-receptor. In terms of Cr(VI), the adsorption performance of N-BLSAC and N-PLAC had little difference. Moreover, N-BLSAC and N-PLAC exhibited an excellent anti-interference property. Therefore, the porous carbon prepared by direct carbonization of BL has significant advantages in removing Cr(VI) and TC from aqueous solution. [Display omitted] • Black liquor was directly used to prepare high surface area activated carbon (N-BLSAC). • The lignin-based porous carbon (N-PLAC) was also prepared for comparison. • The adsorption performance of N-BLSAC was superior to N-PLAC. • The adsorption mechanism of Cr(VI) and TC on N-BLSAC was proposed. [ABSTRACT FROM AUTHOR]

The removal of multiple heavy metal pollutants remains a challenge. Amination and carboxylation modified lignins (NCLs) prepared by one-pot hydrothermal method were used as adsorbents for Cr(VI) and Cd(II) removal. The oxygenous groups content in adsorbents was quantitatively analyzed by Boehm titration in which NCL10 (the mass ratio of citric acid: triethylene diamine = 10) possessed a maximum carboxyl group content of 1.22 mmol/g. The Langmuir adsorption isotherm model was the most suitable, with the highest theoretical adsorption capacity of Cr(VI) and Cd(II) of 1298.6 and 103.1 mg/g, respectively. Meanwhile, FT-IR and XPS exhibited that NCL5 surface contained many functional groups beneficial to the removal of Cr(VI) and Cd(II). The contribution of carboxyl and hydroxyl groups to the removal of Cr(VI) and Cd(II) was quantitatively analyzed. After the blocking of carboxyl and hydroxyl groups, the adsorption rate of Cr(VI) and Cd(II) decreased by 26.4 %, 67.7 % and 7.2 %, 43.3 %, respectively. This study provides effective strategies to overcome the limitations of lignin adsorbents for wastewaters containing a wide range of heavy metal pollutants. [Display omitted] • The amino- and carboxylation-modified NCL5 surface facilitated the adsorption of Cr(VI) and Cd(II) from wastewater. • The content of oxygenous groups in adsorbents was quantitatively analyzed by Boehm titration. • The contribution of carboxyl and hydroxyl groups to the removal of Cr(VI) and Cd(II) was quantitatively analyzed. • The adsorption mechanism of NCL5 on Cr(VI) and Cd(II) was investigated in details. [ABSTRACT FROM AUTHOR]

This work reports a novel citric-acid-assisted sol-gel method that does not contain any template or hazardous chemicals for the electrospinning of mesoporous silicon-magnesium oxide (MgO–SiO 2) ceramic fibers. Citric acid was fully utilized in the preparation of a precursor solution to catalyze tetraethyl orthosilicate (TEOS) hydrolysis, chelate with magnesium ions and cause pore formation during calcination. Moreover, H 2 O 2 addition resulted in fiber decoloration, hydrophilicity, surface area reduction and surface basicity enhancement. The studied mesoporous MgO–SiO 2 ceramic fibers (Si:Mg = 1.5:1 atomic ratio) exhibited good morphologies with diameters of 1.23 ± 0.34 μm and a BET surface area of 142.61 m2‧g−1 after heat-treatment at 600 °C. The adsorption characteristics of the ceramic fiber toward Pb(II), Cu(II), methylene blue (MB) and fulvic acid (FA) were studied. The ceramic fibers showed high adsorption capacities of 753.1/481.0 mg‧g−1 for Pb(II)/Cu(II), which obeyed the pseudo-second-order kinetics and the Langmuir isotherm model. The Freundlich model provided a better fit for the MB and FA adsorption isotherms, and the pseudo-first-order model could describe the kinetics data of FA adsorption. The abnormal kinetics of MB adsorption were observed to follow a pseudo-second-order model at the early phase but then followed a pseudo-first-order model. The innovative strategy of synthesizing MSCFs could contribute to the development of composite oxide ceramic fibers that are relevant to a variety of applications. [ABSTRACT FROM AUTHOR]

• Multifunctional KBiO 3 has physical adsorption, chemical oxidation and photocatalytic abilities. • The multifunctional abilities of KBiO 3 could be facile and controlled regulation through acidification. • Degradation of MB by KBiO 3 was investigated under both dark and light conditions. • KBiO 3 -1.0 improved the MB degradation efficiency by 7.04 times under light condition. In this work, a facile and effective strategy for improving the degradation ability of potassium bismuthate (KBiO 3) was first proposed by using HNO 3 acidification. The degradation ability of methylene blue (MB) by untreated and acidified KBiO 3 was systematically investigated under both dark and light conditions. Under light condition, KBiO 3 exhibited physical adsorption, chemical oxidation, and photocatalysis abilities during the MB degradation. Compared with KBiO 3 -0, the apparent reaction rate constant of KBiO 3 -1.0 (c(HNO 3)/c(KBiO 3) = 1.0) increased by 7.04 times. The specific surface area increased by 2.94 times. In-situ EPR demonstrated that the generation of singlet oxygen (1O 2) was gradually increased with increasing acid addition, which promoted the oxidation degradation of MB. Moreover, according to the photocurrent, EIS, and PL spectra measurements, the separation efficiency of photogenerated electrons and holes was significantly enhanced, indicating the improved photocatalysis ability of KBiO 3. This work provides a deep understanding into the regulation of adsorption, oxidation, and photocatalysis abilities of bismuthate. [ABSTRACT FROM AUTHOR]