Black Liquor Research Articles

Opportunity for valorization of pulping by-product in production high performance sustaining release lignin-based gel

This study focuses on optimizing the pulping by-product to produce effective hydrogels for controlling the release of salicylic acid (SA). In this regard, two routes are achieved: the first involves preparing black liquor (BL) composite hydrogels with various polymer macromolecules [polyacrylamide (PAM), polyvinyl alcohol (PVA), and chitosan (Cs), and the second involves carboxymethylation of BL and grafting with acrylamide. Hydrogels are evaluated using spectral analysis (ATR-FTIR), thermal analysis (TGA and DTG), and swelling measures. Encapsulation, release profile, SA release kinetics, as well as ATR-FTIR and SEM measurements, were used to evaluate the behavior of loaded hydrogels. According to the results, grafted carboxymethylated BL-gel had the maximum SA release (98.7 %), followed by PAM-BL (51.7 %) and PAM/PVA-BL (43.1 %). Over a 48-hour period, the hydrogels demonstrated a prolonged SA release pattern. The Ritger-Peppas and Higuchi models fitted to all examined hydrogels showed that SA release followed both Fickian and non-Fickian diffusion pathways.

Data-driven interpretation, comparison and optimization of hydrogen production from supercritical water gasification of biomass and polymer waste: Applying ensemble and differential evolution in machine learning algorithms

Supercritical water gasification (SCWG) has been utilized for producing hydrogen from organic wastes, which is associated with sustainable development. Nevertheless, identifying the optimal SCWG conditions and appropriate catalysts for diverse waste materials to yield hydrogen-rich syngas is consistently a laborious and costly endeavor. The current research presents a comprehensive framework that combines machine learning models (Decision Tree, Ensembled Learning Tree, Support Vector Machine, and Gradient Boost Regression) with Differential Evolution Optimization (DEO) to predict and optimize hydrogen production from Supercritical Water Gasification (SCWG) using 24 different biomass characteristics and process parameters.The findings indicate that ELA-DEO emerges as the preferred method for forecasting hydrogen yield (R2test = 0.95, RMSETest = 0.091), demonstrating its effectiveness in handling intricate variable-target relationships. Conversely, Support Vector Machine (SVM) displayed weaker performance with an R2Test of 0.73 and RMSETest of 0.116. In the SHAP feature importance analysis, temperature, catalyst amount, catalyst type, hydrogen and oxygen were highlighted as important parameters affecting the process. In addition, by fine-tuning the machine learning hyperparameters, the DEO optimization method was used to maximize the production of H2. The optimized ELA-DEO model was used to identify the ideal features and conditions applicable to our experimental setup. Based on these findings, a recommended biomass table was finally formulated, which was validated by the ELA-DEO model. According to our laboratory results, Dunaliella salina produced 12 mmol of hydrogen with a 35% selectivity. Black liquor with 3% (wt) wood has the capacity to produce 17.21 mmol of hydrogen. Also, when crude glycerol was reacted with RuCl3, 18.7 mmol of hydrogen were generated. However, Dunaliella salina produced a 64% mole fraction of total gas output, which matched the maximum value predicted by our ELA-DEO models.

From waste to resource: Transforming Kraft black liquor into sustainable porous carbon fillers for radome applications

The study addresses environmental and commercial challenges posed by weak black liquor (WBL) generated through the Kraft process in the paper industry. WBL, a toxic waste, annually reaches a staggering 1.3 billion tonnes globally. Currently, it is either incinerated for energy production or subjected to costly and complex chemical treatments to extract valuable compounds. Despite efforts to develop a scalable value-added material, the existing methods are inefficient in fully reusing WBL. Here, we report a simple chemical synthesis process that reuses 100 % of WBL without generating any waste materials; even salts recovered during the process might be reintegrated into the industry as chemical byproducts. Furthermore, given the simplicity and efficiency of the proposed synthesis methodology to transform WBL into a novel and sustainable porous carbon material, the carbon Kraft (CK). The process can also be scaled by using the right synthesis proportions and within a circular economy. CK exhibited desirable characteristics with a renewable content of 65 wt%, including a turbostratic graphitic-like structure (48.8 % graphitized), carbon content of 85 wt%, large specific surface area of 234.0 m2∙g−1, nanoporosity of 0.13 cm3∙g−1, and density of 1.92 g∙(cm3)-1. Moreover, CK showed electrical and thermal insulating characteristics, essential for use as fillers for elastomeric composite in electromagnetic transparent radome structures used to protect antennas and radars of unmanned aerial vehicles (UAV) from harsh environmental effects. Radomes were designed through the electromagnetic impedance match theory of half-wavelength calculations over specific frequencies of 1.3, 10, 15, 20, and 30 GHz. Results showed excellent transmission loss between −0.41 and −1.48 dB, representing 90.8 % and 70.5 % of transmittance, respectively.

Insight mechanism of magnetic activated catalyst derived from recycled steel residue for black liquor degradation

The present work deals with developing a method for revalorizing steel residues to create sunlight-active photocatalysts based on iron oxides. Commercial-grade steel leftovers are oxidized under different combinations of pH and temperature (50–90 °C and 3 ≥ pH ≤ 5) in a low energy-intensive setup. The material with the highest production efficiency (yield > 12%) and magnetic susceptibility (χm = 387 × 10−6 m3/kg) was further explored and modified by diffusion of M2+ (Zn and Co) ions within the structure of the oxide using a hydrothermal method to create ZnFe2O4, CoFe2O4 and combined Co–Zn ferrite. (Co–Zn)Fe2O4 displayed a bandgap of 2.02 eV and can be activated under sunlight irradiation. Electron microscopy studies show that (Co–Zn)Fe2O4 consists of particles with diameters between 400 and 700 nm, homogeneous size, even distribution, and good dispersibility. Application of the developed materials in the sunlight catalysis of black liquors from cellulose extraction resulted in a reduction of the Chemical Oxygen Demand (− 15% on average) and an enhancement in biodegradability (> 0.57 BOD/COD) after 180 min of reaction. Since the presented process employs direct solar light, it opens the possibility to large-scale water treatment and chemical upgrading applications.

N-doped lignin-based activated carbon aerogel derived from bamboo black pulp liquor for efficient removal of malachite green in wastewater.

In this study, a lignin-based aerogel (LA) was prepared through acid precipitation of BPBL, followed by sol-gel method and freeze-drying. Additionally, a one-step activation-carbonization method was used to acquire nitrogen-doped lignin-based activated carbon aerogel (NLACA). The adsorption and catalytic degradation performance for malachite green (MG) were examined. The specific surface area of NLACA after N-doping was 2644.5 m2/g. The adsorption capacity for MG was increased to 3433mg/g with the presence of nitrogenous functional groups on surface of NLACA compared without N-doping. Meanwhile, non-radical singlet oxygen is the primary active substance and degradation efficiency arrives at 91.8% after the catalytic degradation within 20min and it has good stability and reuse. Three possible degradation pathways during degradation were analyzed by LC-MS technique. The adsorption isotherm and kinetic data demonstrated conformity with both the Langmuir model and the pseudo-second-order kinetic model. The primary mechanisms of the adsorption for MG dyes on NLACA include hydrogen bonding, π-π interactions, attraction of electrostatic and pore filling. Hence, NLACA derived from BPBL acts as a cost-effective and high-performance adsorbent and catalyst for removal of MG in dye wastewater. This concept introduces an innovative approach of "treatment of waste with waste" for developing a low-consumption, high-efficiency dye wastewater treatment and provides significant reference to treatment dye wastewater.

The effect of operating conditions on neutral sulphite semi-chemical pulping properties: an industrial pilot plant study

The influence of pulping variables on the pulp and black liquor properties for a neutral sulphite semi-chemical pulping system was investigated in a pilot plant pulping setup situated at an industrial paper mill. Eucalyptus chips were used as raw material and the operating variables were Na2SO3 charge (8–18% w/w on oven-dry wood), Na2CO3 charge (0.5–3.0% w/w on oven-dry wood) and maximum cooking temperature (160–180 °C). Response surface methodology was used to parametrize empirical models to find the optimal conditions for maximizing the short-span compression strength index of the pulp. The derived regression models for the black liquor properties and the pulp hypo number had R2-adjusted values above 0.8 and p-values for overall significance below 0.05. The derived regression models for the handsheet strength properties had R2-adjusted values between 0.3 and 0.45 and p-values for overall significance either below 0.05 or between 0.05 and 0.1. The sulphite charge, followed by the carbonate charge, had the most notable effect on the evaluated properties with the effects of temperature being less significant. Optimization of the pilot plant system showed that the short-span compression strength index of the pulp could be maximized to 26.7 N m/g, using a sulphite charge of 9.4% (w/w on oven-dry wood) and a carbonate charge of 1.94% (w/w on oven-dry wood), similar to short-span compression strength indices typically achieved using other pulping processes.

Lignin extraction in chemical pulp mills: The role of flexible operation

Lignin extracted from black liquor in chemical pulp mills can potentially replace fossil carbon feedstocks in fuels and materials, thereby increasing the economic and environmental added values of woody biomass. However, since lignin extraction reduces the electricity generation of the mill, the added value depends on the characteristics of the electricity market in which the mill operates. In this study, a model mill is exposed to two different electricity price profiles: the low and steady prices of south-central Sweden in Year 2019; and the high and volatile prices of the same region in Year 2022. For the model mill, investments in lignin extraction designed to increase pulp production are economically viable and have low levels of sensitivity to electricity price levels and price volatility. The viability of lignin extraction without increased pulp production depends on the relationship between the electricity and lignin prices. With stable electricity prices, or steady mill operation, a rule-of-thumb holds that for lignin extraction to be viable, the lignin price (€/t) must be 1.8-times the average electricity price (€/MWh) plus 40 €/t for the supply of chemicals. With volatile electricity prices and flexible operation of the recovery boiler, the mill can shift the loss in electricity sales to low-price hours, thereby saving 15–70 % of the operational costs of lignin extraction, as compared to steady operation. This effect can be further enhanced by increasing the capacity of the lignin extraction process or extending the size of the black liquor storage tank. The proposed flexibility measures allow the market-integrated pulp mill to export lignin to replace fossil carbon supplies in other sectors, while supporting the electricity system during hours with high demand and low supply.

Effects of different soda loss measurement techniques on brownstock quality

The efficiency of the kraft recovery plant, bleaching process, and paper machine are affected when black liquor carryover from the brownstock washers is not controlled well. Measuring soda loss within a mill can vary from using conductivity, either in-situ or with a lab sample of black liquor filtrate squeezed from the last stage washer, to measuring absolute sodium content with a lab sodium specific ion probe or spectrophotometer. While measuring conductivity has value in tracking trends in black liquor losses, it is not an acceptable method in reporting losses in absolute units, typically in lb/ton of pulp. This is further complicated when trying to benchmark soda loss performance across a fleet of mills with multiple washer lines. Not only do the testing methods vary, but the amount of bound soda on high kappa pulps can be significant. This variability creates inconsistent results, and studies are needed to understand the effect of different testing methods on the pulp quality. In this study, soda loss is expressed as sodium sulfate (Na2SO4). Four different methods to measure soda content in pulp off commercial brownstock washers were studied: full digestion (FD), washing soaking overnight and washing (WSW), soaking in boiling water and stirring 10-min (SW-10), and squeeze-no wash (Sq). Total, washable, and bound sodium sulfate calculations were determined for each soda content measuring technique using inductively coupled plasma-optical emission spectroscopy (ICP-OES). Results showed bound and washable sodium sulfate amounts significantly depend on which soda measurement technique was used. In addition, the soda results were correlated with the pulp kappa numbers. As the kappa number increases, bound soda increases, regardless of the soda measurement method used. Impacts of high sodium sulfate in brownstock are also discussed.

Maximizing the valorization potential of lignin through optimization of the Soda pulping conditions

The valorization potential of lignin is strongly dependent on the yield that can be obtained during the pulping process as well as its chemical structure. Both of these are determined by factors such as the biomass type, the selected extraction strategy and the employed conditions. Within this study, Miscanthus x giganteus biomass was subjected to systematically varying Soda pulping conditions, i.e., temperature (100 °C – 180 °C), OH– concentration (0.158 mol/L – 1.000 mol/L) and time (60 min – 360 min). These pulping conditions can be combined into a single factor, reflecting the processing severity, which in this work varied from approximately 1 to 5. The resulting black liquor, precipitated lignin, lignin stock solution (i.e., lignin dissolved in the solvent used in the subsequent depolymerization step) and product pool after mild reductive catalytic depolymerization (200 °C, 10 bar H2 initial, 4 h) were thoroughly characterized using a plethora of analysis techniques. Increasing the severity factor of the pulping was found to result in an enhancement of the delignification degree from 25.3 ± 2.6 % to 95.4 ± 9.9 %. However, beyond a severity factor of 3, fragmentation of native ether linkages and condensation reactions start to cause unfavourable changes in the chemical structure of the lignin and depolymerization product pool. Furthermore, these reactions significantly reduce the total mass yield from biomass to depolymerization product pool. An Adaboost model with quadratic base estimator was trained against the experimental data, and subsequently used to optimize the pulping conditions, aiming at a maximum total mass yield with minimal fragmentation and, hence, condensation, of the lignin. The optimum was experimentally validated, which resulted in a lignin with high β-O-4 content (42.7 ± 2.8 linkages per 100 aromatic units) and a total mass yield of 30.9 ± 3.4 wt% and a pulp with a residual lignin content of 8.25 ± 0.94 wt%.

Influences of 2-ethylanthraquinone on lignin degradation in alkaline cooking of Eucalyptus pellita wood

The impact of 2-ethylanthraquinone (2-EAQ) on alkaline cooking of Eucalyptus pellita wood was examined by analyzing pulp yield, kappa number, the structure and weight-averaged molecular weight (Mw) of dissolved lignin in black liquor and residual lignin in pulp (RL). During soda cooking under 23% of active alkaline (AA) condition, adding 0.06% 2-EAQ reduced the kappa number by 12 points compared to cooking without it. The addition of 0.06% 2-EAQ to kraft cooking increased pulp yield by about 4% at about 19 of kappa number compared to the no addition. The analysis of lignin structure by using semiquantitative heteronuclear single quantum correlation nuclear magnetic resonance (HSQC NMR) showed that the addition of 2-EAQ promoted β-ether cleavage during alkaline cooking and reduced peeling reaction of polysaccharides and prevention of the elimination of γ-OH of lignin to form enol ethers and stilbenes. Overall, the addition of 2-EAQ promoted the degradation of lignin to lower molecular weight compounds, with a more pronounced effect observed in soda cooking than in kraft cooking. Under optimal conditions, the delignification efficiency and pulp yield of soda-EAQ pulping were comparable to kraft cooking.

Heteroatom-Doped Carbon Nanomaterials Derived from Black Liquor for Electrochemical Oxygen Reduction Reaction

Heteroatom-Doped Carbon Nanomaterials Derived from Black Liquor for Electrochemical Oxygen Reduction Reaction

Macroporous lignin adsorbents: A bio-sourced tool kit to defuse the Cr(VI) threat in wastewater

Amino-functionalised (triethylenetetramine) macroporous lignin monoliths were produced by curing an emulsion template containing untreated kraft black liquor with oxirane-crosslinkers. These lignin-based adsorbents were tested for the removal of Cr(VI) from water and synthetic waste water. A one-pot rout for their production is presented and their chemical and physical nature was investigated. Produced monoliths were tested in static and continuous adsorption experiments and chromium removal from water and synthetic wastewater was quantified via UV–vis spectroscopy. The nitrogen content of functionalised lignin monoliths reached up to 5.1 wt%, leading to adsorption capacities of up to 897 mg/g at pH = 2, as compared to non-functionalised lignin monoliths with a maximum adsorption capacity of 117 mg/g. The adsorption capacity of lignin monoliths produced is amongst the highest of bio-based materials presented in the literature.

Feasibility of recycling the filtrate from acidified black liquor for alkaline pulping of golden bamboo grass

To reduce energy consumption, a new pulping process called A-D-E-RC (acidification/desalination/electrolysis/recycle-cooking) was developed by a research group in Guangxi University of China. The present work focuses on the step of recycle cooking (RC) to further investigate the technical feasibility of A-D-E-RC methods. Golden bamboo grass was considered as fiber source material for pulp, and it was cooked with the acidic treating of wastewater from black liquor. Then, the pulp obtained from each cooking was made into paper to test the changes in its physical properties. As a result, the pulp yield increased from 43.9% to 50.2%, after re-using acidified black liquor, and the paper’s tear index and tensile index were improved. Therefore, this study demonstrated the feasibility of recycle cooking (RC) fiber materials for pulp applied the acidic treating wastewater from black liquor, and thereby, it further identifies the technical feasibility of A-D-E-RC pulping methods.

Determining the Pulping Conditions and Properties of Unbleached Pulp from Uruguayan Pinus Taeda

Context: In Uruguay, numerous Pinus taeda plantations are at final-turn age, but they still do not have commercial destination and are exported as green-wood logs. For the development of this sector, it is necessary to strive towards a comprehensive processing of this resource. Method: This work focused on analyzing the use of Pinus taeda wood available in the country to produce brown kraft pulp with a kappa number of 80, which can be used to make packaging paper. As raw materials, we employed by-products from the mechanical wood-transformation industry (wood chips and thinning wood) and final-turn wood. Pulping tests were carried out, varying the alkali charge and the H-factor while aiming for a kappa number of 80. The viscosity, pulping, and rejection yield were measured in the pulps, and the pH and residual alkali content were evaluated in black liquor. Results: Based on the results, the best pulping conditions were an active alkali charge of 14% (Na2O) and an H-factor of 1260 for sawmill chips and thinning wood, as well as an active alkali charge of 14% (Na2O) and an H-factor of 1080 for final-turn wood. The pulp obtained with sawmill chips exhibited the most resistant fibers, and the final-turn wood pulp was the most sensitive to the refining process. Under the aforementioned conditions, the paper properties of laboratory-produced pulp are comparable with those of commercial pulp. Conclusions: This indicates that it is technologically possible to produce brown kraft pulp from Uruguayan Pinus taeda wood, with adequate quality to produce packaging paper

PREPARATION AND CHARACTERIZATION OF NANOPARTICLES OF KLASON AND KRAFT LIGNIN FROM Eucalyptus grandis WOOD

This work aimed to prepare and characterize nanoparticles of lignin produced from sawdust (Klason lignin) and black liquor (Kraft lignin), materials considered to be industrial waste. The raw material of this study was Eucalyptus grandis chips. For Klason lignin, the procedures were carried out according to the TAPPI 222 and, for Kraft lignin, the chips were cooked to collect the black liquor, followed by acid precipitation. The nanolignins were obtained by the mechanical process through a mill using passes from 2, 8 and 13. The characterization of nanolignins was performed by scanning electron microscopy with elemental chemical analysis and transmission electron microscopy, granulometry analysis, thermogravimetric analysis and differential scanning calorimetry. Scanning electron microscopy and transmission electron microscopy showed irregular nanostructures of various shapes and spherical structures, the latter of which were more evident and frequent in Kraft nanolignin. The elemental chemical analysis showed that the washing process of the nanolignins was satisfactory, as only a small percentage of sulfur was detected in the samples. The granulometric measurement confirmed that the nanolignins had nanometric dimensions. Thermal analysis showed the nanolignins had three degradation bands, attributed to the drying of the samples and also to the degradation of hemicelluloses and lignin itself. Therefore, it was possible to confirm the obtainment of Klason and Kraft nanolignins through the use of the mill, and that an increasing number of passes produced a greater portion of particles with nanometric size.

Flame-retardant performance of a novel lignin-based rigid polyurethane foam prepared from pulping black liquor

To improve the flame retardancy of rigid polyurethane foam (RPUF), black liquor lignin-based rigid polyurethane foam (LRPUF) was prepared in this work through a one-step foaming method using lignin and inorganic salt in black liquor lignin as the structural modifier and the additive flame retardant, respectively. Effect of the addition of carbon dioxide treated black liquor lignin (CBL) on the structure and flame retardancy of LRPUF, as well as the flame flame-retardant mechanism of LRPUF, were investigated. The limiting oxygen index (LOI) test and cone calorimetric tests showed that compared to the RPUF, the LOI of LRPUF with 40 wt% CBL increased from 18.9 % to 21.3 %, and the peak heat release rate, total heat release, and total smoke production decreased by 19.5 %, 25.3 %, and 20.5 %, respectively, indicating that the addition of CBL improved the flame retardancy of LRPUF. The flame-retardant mechanism was investigated by analyzing the structure and components of the char residue. We found that a dense protective layer, consisted of char residue and a considerable amount of sodium sesquicarbonate on the surface of the char residue, was formed after combustion. This study provided a novel strategy for the resource utilization of black liquor lignin.

Effective Removal of Pb(II) from Multiple Cationic Heavy Metals—An Inexpensive Lignin-Modified Attapulgite

To develop cost-effective heavy metal adsorbents, we employed water-soluble lignin from black liquor to modify activated attapulgite, resulting in the creation of a novel adsorbent called Lignin-modified attapulgite (LATP). In this study, scanning electron microscopy and Fourier transform infrared spectrometer techniques were utilized to characterize the structural details of LATP. The results revealed that lignin occupies the micropores of attapulgite, while additional functional groups are present on the attapulgite surface. We conducted adsorption tests using LATP to remove five types of heavy metal ions (Cd2+, Pb2+, Zn2+, Mn2+, Cu2+), and it was found that LATP exhibited greater removal mass and binding strength for Pb(II) compared to the other ions. For further investigation, batch experiments were performed to evaluate the adsorptive kinetics, isotherms, and thermodynamics of Pb2+ removal from aqueous solutions using LATP. The results indicated that the adsorption capacity of Pb(II) on LATP decreased with decreasing pH, while the presence of Na+ had no effect on adsorption. The adsorption process reached equilibrium rapidly, and the Langmuir adsorption capacities increased with temperature, measuring 286.40 mg/g, 315.51 mg/g, and 349.70 mg/g at 298 K, 308 K, and 318 K, respectively. Thermodynamic analysis revealed positive values for ΔH0 and ΔS0, indicating an endothermic and spontaneous adsorption process. Furthermore, ΔG0 exhibited negative values, confirming the spontaneous nature of the adsorption. Consequently, LATP demonstrates great potential as an effective adsorbent for the removal of Pb(II). Therefore, LATP shows great potential as an effective adsorbent for the removal of Pb(II) from natural water environments, contributing to the sustainable development of man and nature.

Comparison of thermal, rheological properties of Finnish Pinus sp. and Brazilian Eucalyptus sp. black liquors and their impact on recovery units

Black liquor (BL) is the major bioproduct and biomass fuel in pulp mill processes. However, the high viscosity of BL makes it a challenging material to work with, resulting in issues with evaporators and heat exchangers during its transport and processing. The thermal and rheological properties of BLs from Pinus sp. (PBL) and Eucalyptus sp. (EBL) were studied. FTIR spectra revealed the presence of the characteristic functional groups and the chemical composition in liquors. TGA/DTG curves showed three characteristic degradation stages related to evaporation of water, pyrolysis of organic groups, and condensation of char. Rheologically, liquors are classified as non-Newtonian and with comportment pseudoplastic. Their rheological dynamic shear properties included a linear viscoelastic region up to 1% shear strain, while frequency sweeps showed that storage modulus (Gʹ) > loss modulus (Gʹʹ), thus confirming the solid-like behavior of both BLs. The rheological study demonstrated that increasing the temperature and oscillatory deformations of PBL and EBL decreased their degree of viscoelasticity, which could favor their pumping and handling within the pulp mill, as well as the droplet formation and swelling characteristics in the recovery furnace.

Enhancing the valorization of pulping black liquors in production effective aerogel–carbon nanostructure as adsorbents toward cationic and ionic dyes

This work deals with promoting the efficiency of removing the cationic and ionic dyes by new aerogel–carbon nanostructures. For cleaner production the rice straw-pulping black liquors, which regards serious environmental risk during routine disposing, is used in preparing the aerogel precursors. These aerogels (AGBs) depend on using pulping black liquor in hybrid with resorcinol and the less carcinogenic formaldehyde butyraldehyde. Black liquors from five pulping processes are used, Elemental, thermogravimetric (TGA and DTG), and FTIR-ATR analyses are used to characterize the carbon precursors. While their adsorption behavior toward cationic and anionic dyes are accessed via iodine-value, adsorption capacity and kinetic models, textural characterization, and SEM. The TGA measurements reveal that AGBs from BLs of neutral sulfite and soda-borohydride pulping reagents have higher activation and degradation energies than other aerogels. In terms of cationic and anionic dyes adsorption as well as textural characterization, the AGB-CNSs surpass that made from BLs. The discarded KOH/NH4OH black liquor is used to synthesize the best aerogel precursor for producing cationic methylene blue dye (MB) adsorbent, where it provides an adsorption capacity 242.1 mg/g. The maximum anionic brilliant blue dye (BB) adsorption capacity, 162.6 mg/g, is noticed by Kraft BL-aerogel-CNSs. These finding data overcome the literature carbon adsorbents based on lignin precursors. All examined CNSs toward MB dye follow the Langmuir adsorption equilibrium; while primarily the Freundlich model for BB dye. The pseudo-second-order kinetic model well fits the adsorption kinetics of investigated AGB-CNSs. The textural characterization and SEM revealed a mixture of mesoporous and micro porous features in the CNSs.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite derived from lignin: an efficient peroxymonosulfate activator for naphthalene degradation.

A novel 3D nitrogen-doped porous carbon supported Fe-Cu bimetallic nanoparticles composite (Fe-Cu-N-PC) was prepared via direct pyrolysis by employing black liquor lignin as a main precursor, and it was utilized as a novel catalyst for PMS activation in degrading naphthalene. Under the optimum experimental conditions, the naphthalene degradation rate was up to 93.2% within 60 min in the Fe-Cu-N-PC/PMS system. The porous carbon framework of Fe-Cu-N-PC could facilitate the quick molecule diffusion of reactants towards the inner bimetallic nanoparticles and enriched naphthalene molecules from the solution by a specific adsorption, which increased the odds of contact between naphthalene and reactive oxygen species and improved the reaction efficiency. The quenching reaction proved that the non-free radical pathway dominated by 1O2 was the main way in naphthalene degradation, while the free radical pathway involving SO4·- and ·OH only played a secondary role. Moreover, owing to its high magnetization performance, Fe-Cu-N-PC could be magnetically recovered and maintained excellent naphthalene degradation rate after four degradation cycles. This research will offer a theoretical basis for the construction of facile, efficient, and green technologies to remediate persistent organic pollutants in the environment.