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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]

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/HO. Gel permeation chromatography showed a significant increase in weight-average molecular weight ( M) 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 (H-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, M 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 H-NMR spectra indicated. Moreover, the HRP/HO incubation induced a significant improvement in the adsorption and dispersion properties of LSs. Therefore, the HRP/HO incubation is a promising approach for industrial applications of LSs. [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]

An environmentally friendly lignin-based composite (Lignin-PEI) was facilely prepared via cross-linking enzymatic hydrolysis lignin matrix and branched poly (ethylene imine). The specific physicochemical and structural properties of lignin-PEI were characterized by elemental analysis, N 2 physisorption, GPC, TG, SEM, FT-IR and XPS. The nitrogen content of lignin-PEI was 9.02%, and the BET surface area was 20.32 m2/g. The synthetic composite showed high capacity and selectivity of Cr(VI) adsorption. The influence of solution pH, contact time, initial Cr(VI) concentration, and coexisting ions on Cr(VI) adsorption on lignin-PEI was systemically studied. The Cr(VI) adsorption on lignin-PEI was well described by the Langmuir model. According to the Langmuir model, the Cr(VI) adsorption capacity on lignin-PEI was as high as 898.2 mg/g at 318 K and pH 2.0. The calculated thermodynamic parameters, such as Δ G , Δ H , and Δ S , indicated the spontaneous and endothermic adsorption of Cr(VI) on lignin-PEI. The adsorption of Cr(VI) by lignin-PEI was following the pseudo-second-order kinetic model, indicating that it was a chemisorption process. The uptake mechanism was demonstrated to be electrostatic attraction, ion exchange, complexation and partial reduction. This work provided a promising candidate for Cr(VI) uptake with lignin-based biosorbents. Unlabelled Image • An eco-friendly lignin-based biosorbent was prepared by grafting PEI. • The maximum adsorption capacity of Cr(VI) was 898.2 mg/g. • Lignin-PEI had an excellent selectivity for Cr(VI). • The adsorption mechanism was proposed. [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]

Background: Cellulase adsorbed on cellulose is productive and helpful to produce reducing sugars in enzymatic hydrolysis of lignocellulose; however, cellulase adsorbed on lignin is non-productive. Increasing productive adsorption of cellulase on cellulose would be beneficial in improving enzymatic hydrolysis. Adding lignin that was more hydrophilic in hydrolysis system could increase productive adsorption and promote hydrolysis. However, the effect mechanism is still worth exploring further. In this study, lignosulfonate (LS), a type of hydrophilic lignin, was used to study its effect on cellulosic hydrolysis. Results: The effect of LS on the enzymatic hydrolysis of pure cellulose (Avicel) and lignocellulose [dilute acid (DA) treated sugarcane bagasse (SCB)] was investigated by analyzing enzymatic hydrolysis efficiency, productive and non-productive cellulase adsorptions, zeta potential and particle size distribution of substrates. The result showed that after adding LS, the productive cellulase adsorption on Avicel reduced. Adding LS to Avicel suspension could form the Avicel–LS complexes. The particles were charged more negatively and the average particle size was smaller than Avicel before adding LS. In addition, adding LS to cellulase solution formed the LS–cellulase complexes. For DA-SCB, adding LS decreased the non-productive cellulase adsorption on DA-SCB from 3.92 to 2.99 mg/g lignin and increased the productive adsorption of cellulase on DA-SCB from 2.00 to 3.44 mg/g cellulose. Besides, the addition of LS promoted the formation of LS–lignin complexes and LS–cellulase complexes, and the complexes had more negative charges and smaller average sizes than DA-SCB lignin and cellulase particles before adding LS. Conclusions: In this study, LS inhibited Avicel's hydrolysis, but enhanced DA-SCB's hydrolysis. This stemmed from the fact that LS could bind cellulase and Avicel, and occupied the binding sites of cellulase and Avicel. Thus, a decreased productive adsorption of cellulase on Avicel arose. Regarding DA-SCB, adding LS, which enhanced hydrolysis efficiency of DA-SCB, increased the electrostatic repulsion between DA-SCB lignin and cellulase, and therefore, decreased non-productive adsorption of cellulase on DA-SCB lignin and enhanced productive adsorption of cellulase on DA-SCB cellulose. [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]

• Electrospinning of SiO 2 -MgO hybrid fibers (SMHFs) for the first time. • High-pressure steam pretreated SMHFs have high S BET and adsorption capacity. • The affinity sequence of tested ions was Pb(II)>Cu(II)>Ni(II)>Cd(II)>Zn(II). • Maximum capacities of 787.9 and 493.0 mg g−1 for Pb(II) and Cu(II) at 298 K. • Spontaneous and physicochemical adsorption nature of SMHFs for Pb(II) and Cu(II). SiO 2 -MgO hybrid fibers (SMHFs) were fabricated by one-step electrospinning process, characterized, and evaluated in heavy metal adsorption, for the first time. High-pressure steam (HPS) pretreated SMHFs showed high specific surface area (S BET) and large number of surface basic sites accompanied by the crystallization of MgO. The SMHFs showed high affinities for Pb(II) and Cu(II) with the distribution coefficients K d >100 L·g−1 (when pH > 4). Langmuir model and pseudo-second-order kinetic model described the experimental data well, and the maximum adsorption capacities of 787.9 and 493.0 mg·g−1 for Pb(II) and Cu(II) at 298 K were the highest among those of reported SiO 2 -MgO adsorbents. Thermodynamics indicated SMHFs had the spontaneous and physicochemical adsorption nature. SMHFs kept good capacities in the presence of interfering substances and retained their reusability. The SMHFs with the superiority of high efficiency, low cost, easy preparation and environmentally benign, have promising applications in wastewater treatment and relative fields. [ABSTRACT FROM AUTHOR]