Concentration Of Surface Functional Groups Research Articles

Untapped potential of food waste derived biochar for the removal of heavy metals from wastewater

The presence of heavy metals in water pose a serious threat to both public and environmental health. However, the advances in the application of low cost biochar based adsorbent synthesize from various feedstocks plays an effective role in the of removal heavy metals from water. This study implies the introduction of novel method of converting food waste (FW) to biochar through pyrolysis, examine its physiochemical characteristics, and investigate its adsorption potential for the removal of heavy metals from water. The results revealed that biochar yield decreased from 18.4 % to 14.31 % with increase in pyrolysis temperature from 350 to 550 °C. Likewise, increase in the pyrolysis temperature also resulted in the increase in the ash content from 39.87 % to 42.05 % thus transforming the biochar into alkaline nature (pH 10.17). The structural and chemical compositions of biochar produced at various temperatures (350, 450, and 550 °C) showed a wide range of mineralogical composition, and changes in the concentration of surface functional groups. Similarly, the adsorption potential showed that all the produced biochar effectively removed the selected heavy metals from wastewater. However a slightly high removal capacity was observed for biochar produced at 550 °C that was credited to the alkaline nature, negatively charged biochar active sites due to O-containing functional groups and swelling behavior. The results also showed that the maximum adsorption was recorded at pH 8 at adsorbent dose of 2.5 g L−1 with the contact time of 120 min. To express the adsorption equilibrium, the results were subjected to Langmuir and Freundlich isotherms and correlation coefficient implies that the adsorption process follows the Freundlich adsorption isotherm. The findings of this study suggest the suitability of the novel FW derived biochar as an effective and low cost adsorbent for the removal of heavy metals form wastewater.

Sewage Sludge-Derived Biochar and Its Potential for Removal of Ammonium Nitrogen and Phosphorus from Filtrate Generated during Dewatering of Digested Sludge

Utilizing waste, such as sewage sludge, into biochar fits the circular economy concept. It maximizes the reuse and recycling of waste materials in the wastewater treatment plant. The experiments were conducted to assess: (1) the impact of the temperature on the properties of biochar from sewage sludge (400 °C, 500 °C, 600 °C, 700 °C); (2) how the physical activation (CO2, hot water) or chemical modification using (MgCl2, KOH) could affect the removal of ammonia nitrogen and phosphorus from filtrate collected from sludge dewatering filter belts or synthetic solution, wherein the concentration of ammonium nitrogen and phosphorus were similar to the filtrate. Based on the Brunner–Emmett–Teller (BET) surface and the type and concentration of surface functional groups for the second stage, biochar was selected and produced at 500 °C. The modification of biochar had a statistically significant effect on removing nitrogen and phosphorus from the media. The best results were obtained for biochar modified with potassium hydroxide. For this trial, 15%/17% (filtrate/synthetic model solution) and 72%/86% nitrogen and phosphorus removal, respectively, were achieved.

Preparation of biochars by conventional pyrolysis of herbal waste and their potential application for adsorption and energy purposes.

The nettle, sage, mint and lemon balm herbs were used for biochars preparation. The physicochemical parameters of obtained materials were related to the lignocellulose composition of the precursors. It has been proved that the content of mineral substance has a significant influence on development of surface area, whereas the amount of hemicellulose affects the content of surface functional groups. It has been also shown that the obtained biochars are characterized by great energy parameters. The higher heating values (HHV) of the carbonaceous materials are comparable to the typical energy sources. The greatest HHV value (20.36 MJ/kg) was characteristic for the biochar obtained by pyrolysis of the lemon balm. In addition, the biochars were used for ionic polymers adsorption from one- and two-components solutions. Despite the adsorbed amounts of macromolecules are not great is has been proved that polyethylenimine and polyacrylic acid have positive influence on their mutual adsorption.

Efficient Adsorption of Ammonia by Surface-Modified Activated Carbon Fiber Mesh.

In view of the characteristics and risks of ammonia, its removal is important for industrial production and environmental safety. In this study, viscose-based activated carbon fiber (ACF) was used as a substrate and chemically modified by nitric acid impregnation to enhance the adsorption capacity of the adsorbent for ammonia. A series of modified ACF-based adsorbents were prepared and characterized using BET, FTIR, XPS, and Boehm titration. Isotherm tests (293.15 K, 303.15 K, 313.15 K) and dynamic adsorption experiments were performed. The characterization results showed that impregnation with low concentrations of nitric acid not only increased the surface acidic functional group content but also increased the specific surface area, while impregnation with high concentrations of nitric acid could be able to decrease the specific surface area. ACF-N-6 significantly increased the surface functional group content without destroying the physical structure of the activated carbon fibers. The experimental results showed that the highest adsorption of ammonia by ACFs was 14.08 mmol-L-1 (ACF-N-6) at 293 K, and the adsorption capacity was increased by 165% compared with that of ACF-raw; by fitting the adsorption isotherm and calculating the equivalent heat of adsorption and thermodynamic parameters using the Langmuir-Freundlich model, the adsorption process could be found to exist simultaneously. Regarding physical adsorption and chemical adsorption, the results of the correlation analysis showed that the ammonia adsorption performance was strongly correlated with the carboxyl group content and positively correlated with the relative humidity (RH) of the inlet gas. This study contributes to the development of an efficient ammonia adsorption system with important applications in industrial production and environmental safety.

A Study of V(IV/V) and V(II/III) Reactions on Carbon Based Electrodes

The vanadium redox flow battery (VRFB) is one of the most promising energy storage technologies for large scale commercialization. Carbon based electrodes, such as carbon felts or carbon paper, are used for V(II/III) and V(IV/V) reactions. To improve the vanadium redox reaction kinetics, the carbon electrodes are usually activated by a variety of methods such as thermal treatment, heteroatom doping, catalyst incorporation etc. [1] It is generally considered that surface functional group such as C–OH, C=O play an important role in vanadium redox reaction [1-6]. Even though there are reports showing higher surface functional group content e.g. total C–O content leads to improved vanadium redox reaction kinetics [2-6], qualitative correlation of the surface property of the carbon materials and the vanadium redox reaction is not reported. There is a need for fundamental understanding of the surface properties of the carbon electrodes and their relation with the reaction kinetics, including the key parameters that determine them.In this work, using cyclic voltammetry (CV), we studied the surface properties of a variety of carbon based electrodes (glassy carbon (GC), edge plane pyrolytic graphite, base plane pyrolitic graphite, graphite (from Pine Research, called graphite-Pine thereafter), graphite rod, and H2SO4 soaked graphite rod), and the V(II/III) and V(IV/V) reaction kinetics on these electrodes. The goal of soaking the graphite rod electrode in H2SO4 is to activate the electrode and make it comparable to the carbon felt electrode [1]. XPS was also used to analyze the functional group. The relationship between the surface properties and the reaction kinetic parameters was analyzed.Fig. 1 compares the cyclic voltammograms (CV) of the edge plane, basal plane graphite and GC electrodes in 2 M H2SO4. Two redox couples are observed, ascribed to C=O and COOH group redox peak respectively [7]. On basal plane electrode, these two redox peaks are less significant, and an extra reduction peak is observed at 0.24 V due to the C–OH reduction. On the GC electrode, the C=O redox peak is still discernable but the COOH redox peak is almost undetectable. A capacitance region appears between 0.6 – 0.75 V vs Ag/AgCl for all these electrodes. Similar features are observed with the graphite-Pine, graphite rod and H2SO4 soaked graphite rod electrodes with significantly enhanced redox peaks and larger capacitance. The H2SO4 soaked graphite rod electrode presents the highest surface functional group density and capacitance. XPS also shows that the H2SO4 soaked graphite rod electrode has the highest total C–O content.CV of V(IV/V) and V(II/III) were measured using these electrodes at different scan rates. Fig. 2 shows the CV of V(IV/V) reaction on these electrodes. The three graphite rod electrodes show better reversible feature than the edge plane, basal plane and GC electrodes. Diffusion coefficient, transfer coefficient and reaction rate constant were obtained from the CVs. The diffusion coefficient follows the sequence of soaked graphite rod > graphite rod > Graphite-Pine > Edge plane > GC > basal plane electrode. The transfer coefficient and reaction rate constant are also different for these electrodes. Similarly, the diffusion coefficient, transfer coefficient and reaction rate constant are obtained for the V(II/III) reaction. The diffusion coefficient and reaction rate constant for the V(II/III) reaction are smaller than that for the V(IV/V) reaction on the corresponding electrodes. For both V(IV/V) and V(II/III), a linear relationship was found for diffusion coefficient versus the logarithm of capacitance and C=O group functional group. Higher value of log(capacitance) and log(C=O density) leads to larger diffusion coefficient. However, there is no clear relationship between transfer coefficient, reaction rate constant vs capacitance or C=O density. It seems that the capacitance and C=O functional group density are the importance parameters determining the vanadium redox reaction kinetics.References He, Y. Lv, T. Zhang, Y. Zhu, L. Dai, S. Yao., W. Zhu, L. Wang, Chem. Eng. J., 427 (2022) 131680Zhang, J. Xia, Z. Li, H. Zhou, L. Liu, Z. Wu, X. Qiu, Electrochim. Acta 89 (2013) 429– 435Liu, L. Yang, Q. Xu, C. Yan, RSC Adv., 2014, 4, 55666Choi, H. Noh, S. Kim, R. Kim, R. Kim, J. Lee, J. Heo, H.-T. Kim, J. Energy Storage, 21 (2019) 321 – 327Eifert, R. Banerjee, Z. Jusys, R. Zeis, J. Electrochem. Soc., 165 (2018) A2577 – A2586Leuna, D. Priyadarshani, A. K. Tripathi, M. Neergat, J. Electroanal. Chem., 878 (2020) 114590K. Singh, M. Pahlevaninezhad, N. Yasri, E. P. L. Roberts, ChemSusChem 2021, 14, 2100–2111 Figure 1

Effects of a gasoline particulate filter on the physicochemical characteristics of particulate matter from a gasoline engine

Gasoline particulate filters (GPFs) are being used increasingly in gasoline direct-injection engines because they can reduce particle emissions and allow emission regulations to be met. Therefore, understanding the particles' physicochemical properties can help with optimizing the post-processing systems and engine calibration. In this study, particles were collected both pre- and post-GPF using a Dekati® low-pressure impactor and a quartz-fiber filter membrane. High-resolution transmission electron microscopy was used to observe the morphologies of the particles, the fractal dimension was used to quantify the aggregate structure, and an image-processing program developed in MATLAB was used to analyze the nanostructures of the primary particles. Raman spectroscopy was used to study the order degree of the particles’ carbon crystal arrangement, and Fourier transform infrared spectroscopy was used to assess the changes in their surface functional-group content. After the particles were graded according to particle size, it was found that (i) the fractal dimension of all size levels and (ii) the average size of the primary particles were both smaller post-GPF than pre-GPF. Post-GPF, there was a higher proportion of nucleated particles, the particle fringe length was shorter, the tortuosity and separation were both greater, the particles were more disordered, the ratio of C–H to C–O was greater, and the proportion of organic composition of the particles and their oxidation activity were both increased.

Study on the variation law of geometric and surface properties of ultrafine coal particles with particle size

The variation of particle properties and surface physicochemical properties during coal crushing was studied. The geometric properties of coal particles were explored by analyzing the particle size distribution curve under the dual-domain fractal rule and the surface morphology under the scanning electron microscope. With the increased refinement degree, the fine particle size gradually concentrated and uniform, and the population difference of coarse particle size increased. The dominant force for particle refinement transitioned from shear force to crushing force, and the angular coal particles gradually had roundness and aggregation of ultrafine particles appeared. The surface properties of the particles were analyzed by the surface pore structure, the surface functional group content and the charge state. The specific surface area and average pore size of the coal particles gradually increased, and the adsorption kinetic constant gradually decreased, indicating that the crushing exposed the new surface and made the micro pores more developed. The oxygen-containing functional groups on the surface gradually decreased and the isoelectric point gradually increased, indicating that the hydrophobicity of the particles decreased gradually during the refinement process.

Influence of Supercritical CO2 Fluid on CH4 and CO2 Diffusion in Vitrinite-Rich Coals and Inertinite-Rich Coals

Coal maceral composition has a great effect on gas adsorption and diffusion. The interaction between maceral composition and supercritical CO2 (SCCO2) fluid will affect gas diffusion behavior in coals. Thus, the diffusivity derived from adsorption kinetics of CH4 and CO2 in vitrinite- and inertinite-rich coals with low-violate bituminous rank collected from the Hancheng mine of the Weibei coalfield pre- and post-SCCO2 fluid exposure (SFE) were tested at the conditions of 45 °C and 0.9 MPa. In combination with pore distribution and functional group content, the possible mechanism of the alterations in gas diffusion characteristics in coals with various maceral compositions was addressed. The results show that for vitrinite-rich coals, SFE increases the macropore apparent diffusion coefficient of CH4, while this treatment decreases the micropore apparent diffusion coefficient of CH4. However, the reverse trend is found for CO2 diffusion–adsorption rate. For inertinite-rich coals post-SFE, CH4 diffusion–adsorption rate increases, while an increase and a decrease in diffusivity CO2 occur for macropore and micropore, respectively. Generally, SFE shows a stronger impact on CO2 adsorption rate than CH4 in coals. The results suggest that the diffusion of CH4 and CO2 in coals with different maceral compositions show selectivity to SCCO2 fluid. The possible reason can be attributed to the changes in pore structure and surface functional group content. SFE causes an increase in macro/mesopore volume of all samples. However, SFE induces a reduction in oxygen-containing species content and micropore volume of inertinite-rich coals, while the opposite trend occurs in vitrinite-rich coals. Thus, the changes in pore volume and surface functional group account for the difference in gas diffusivity of coals with different maceral compositions. With regard to the micropore diffusion–adsorption behavior of CH4 and CO2, the impact of oxygen-containing species is superior to pore volume. The oxygen-containing species favor CO2 diffusion–adsorption but go against CH4 transport. This effect accounts for the reduction in the micropore diffusion–adsorption rate of CH4 and the increase in micropore diffusivity of CO2 in vitrinite-rich coals, respectively. However, the aforementioned effect is the opposite for inertinite-rich coals. Overall, the changes in gas diffusion in coals with different maceral composition during the CO2-ECBM process requires further attention.

Effect of NaNO2 Reductant Pretreatment on Low-Rank Coal Flotation.

As the reserves of high-quality coal resources in China are decreasing, it is imperative to improve the processing and comprehensive utilization of low-rank coal. In this study, NaNO2 was used for the flotation pretreatment test of the low-rank coal obtained from Majialiang, and the mechanism was discussed by contact angle analysis, zeta potential measurements, and XPS peak fitting analysis. The results showed that when the dosage of NaNO2 was 2000 g/t and the pretreatment time was 5 min, the flotation effect was the best, the ash contents of concentrate ash and tailings and the combustible recovery were 17.15, 37.12, and 42.23%, respectively; the combustible recovery increased by 12%. The contact angle, surface functional group content, and zeta potential measurements showed that with the change of NaNO2 dosage, the content of the hydrophobic functional group and the zeta potential value were consistent with the change of combustible recovery. The increase of hydrophobic functional groups can effectively enhance the hydrophobic interaction on the surface of the coal, which is conducive to the combination of collector and coal, and improve the efficiency of the collector. The NaNO2 pretreatment test can promote flotation efficiency, and the addition of reductant is an effective method for the flotation efficiency of low-rank coal in reducing oxygen-containing functional groups on the surface of low-rank coal to improve the poor floatability. In this study, the method of chemical pretreatment is put forward to provide a new idea for slime flotation.

Evaluation of Interfacial Shear Strength Healing Efficiency between Dynamic Covalent Bond-Based Epoxy and Functionalized Fiberglass

Extending the service life of light-weight composite materials used in structural applications has drawn extensive research interests in recent years. One promising solution is the incorporation of self-healing polymers as the matrix component to enable the intrinsic repair of structural damage, thus allowing the composite structure to maintain its mechanical performance and expand its useful life. One of the primary failure mechanisms in composites is interfacial failure, and this research seeks to develop a methodology that enables reformation of covalent crosslinks at the interface to recover material strength. The approach developed here focuses on the evaluation of interfacial shear strength (IFSS) of a composite material system consisting of a self-healing matrix formed by bisphenol-F diglycidyl ether mixed with 4-aminophenyl disulfide (4-AFD) and fiberglass. Interfacial damage is repaired through thermal stimulus that cleaves the dynamic covalent disulfide bonds in the 4-AFD constituent of the matrix followed by bond reformation to return material strength. The extent of interfacial healing was characterized through repeated microdroplet testing and was measured to be 61.7 and 39.7% for once- and twice-healed microdroplets, respectively, thus demonstrating the potential of the chosen composite system to not only exhibit matrix healing, as reported in most studies, on self-healing composites but also at the fiber–matrix interface. The surface chemistry of the glass fibers was modified through silane coupling agents 3-(glycidoxypropyl)trimethoxysilane and bis(triethoxysilylpropyl)tetrasulfide (Si-69) functionalization, and their subsequent effects on the IFSS and healing efficiency of the fiber–matrix system were investigated. The Si-69-functionalized fiberglass exhibited an enhancement in IFSS of 31.5% due to the improved fiber–matrix chemical interactions because of the increase in surface functional group concentrations. Therefore, this work demonstrates the interfacial healing potential of 4-AFD-based polymer matrices when incorporated in glass fiber composites and highlights the promising effects of surface functionalization for simultaneously improving IFSS and maintaining interfacial healing efficiency.

Physicochemical Characterization of Cherry Pits-Derived Biochar.

Although the suitability of some biochars for contaminants’ sorption separation has been established, not all potential feedstocks have been explored and characterized. Here, we physicochemically characterized cherry pit biochar (CPB) pyrolyzed from cherry pit biomass (CP) at 500 °C, and we assessed their As and Hg sorption efficiencies in aqueous solutions in comparison to activated carbon (AC). The basic physicochemical and material characterization of the studied adsorbents was carried out using pH, electrical conductivity (EC), cation exchange capacity (CEC), concentration of surface functional groups (Boehm titration), and surface area (SA) analysis; elemental C, H, N analysis; and Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX). AsO43− anions and Hg2+ cations were selected as model contaminants used to test the sorption properties of the sorption materials. Characterization analyses confirmed a ninefold increase in SA in the case of CPB. The total C concentration increased by 26%, while decreases in the total H and N concentrations were observed. The values of carbonate and ash contents decreased by about half due to pyrolysis processes. The concentrations of surface functional groups of the analyzed biochar obtained by Boehm titration confirmed a decrease in carboxyl and lactone groups, while an increase in phenolic functional groups was observed. Changes in the morphology and surface functionality of the pyrolyzed material were confirmed by SEM–EDX and FTIR analyses. In sorption experiments, we found that the CPB showed better results in the sorption separation of Hg2+ than in the sorption separation of AsO43−. The sorption efficiency for the model cation increased in the order CP < CPB < AC and, for the model anion, it increased in the order CPB < CP < AC.

Improving the Electrochemical Performances of Supercapacitors through Modification of the Particle Size Distribution of the Carbon Electrode

The effect of a synergetic mixture of large and small activated carbon composite particles on the performance of organic electrolyte-based EDLCs was examined in this work. Different surface areas, pore volumes, particle size distributions, and concentrations of surface functional groups were observed in bi-modal particle sizes of activated carbon composites. Using galvanostatic cycling, the cell capacitance of an activated carbon composite rose with an increase in the fraction of big particles (C8) over a wide range of rates. Due to their moderate specific surface areas, a relatively low fraction of smaller particle size, low concentration of oxygen functional groups, low contact resistance, and high ionic conductivity, the 0.25C4+0.75C8 carbon electrode composite has a high specific capacitance, high retention of high rate discharge, and long cycle life when compared to other composites and single carbon electrodes (C4, C8, and C12). The leakage current and gas evolution may be suppressed to an operating voltage of 3.0 V with an appropriate fraction of large and small particle composition on the carbon electrode, boosting the carbon cells’ reliability and stability.

Surface modification and in situ carbon intercalation of two-dimensional niobium carbide as promising electrode materials for potassium-ion batteries

Potassium ion batteries (KIBs) have a great potential in large scale energy storage because of their cost advantages and similar working mechanism to lithium ion batteries (LIBs). However, the larger ionic radius of K+ presents great challenges to find suitable electrode materials for K+ insertion/extraction. Herein, the surface-modified and in-situ carbon-intercalated Nb2CTx MXene is rationally designed and synthesized as electrode for KIBs. The as-prepared Nb2C/C has larger effective interlayer distance (i.e. gallery height), higher specific surface area and electrical conductivity, and lower concentration of surface functional groups. As a result, Nb2C/C exhibits a significantly increased coulombic efficiency (67.6% for Nb2C/C, 28.5% for Nb2CTx) and its specific capacity is two times higher than that of Nb2CTx at 0.02 A·g−1, three times at 0.1 A·g−1. The Nb2C/C delivers an initial specific capacity of 397.9 mAh·g−1 at 0.02 A·g−1 and 338.1 mAh·g−1 at 0.1 A·g−1, and maintains 80.0% after 100 cycles at 0.02 A·g−1 and 76.2% after 200 cycles at 0.1 A·g−1, respectively. Notably, Nb2C/C possesses outstanding cyclic stability and rate performance at various current densities, outperforming most of reported MXene-based anodes for KIBs. The excellent potassium storage performance of Nb2C/C can be ascribed to the abundant active sites exposed to electrolyte, rapid diffusion kinetics of K+ and few side reactions at the electrode/electrolyte interface. This work proposes an effective strategy for the MXene-based materials to maximize their potential applications in various fields such as batteries, supercapacitors and catalysts.

Morphology and surface hydroxyl engineering of H4Nb6O17 nanotubes for enhanced ethyl mercaptan removal

Ethyl mercaptan is usually present in natural gas and biogas, and must be removed due to its toxic, malodorous and corrosive properties. The characteristics content of surface functional groups plays a vital role for the adsorption performance of the adsorbent. In present study, a facile method was proposed to adjust the morphology and structure, as well as the amount of the surface hydroxyl groups of H4Nb6O17 nanotubes. The synthesis of H4Nb6O17 nanotubes with different morphology and structure can adjust the content of surface hydroxyl groups by controlling the flocculation process of [Nb6O17]4- nanosheet sol. By reducing the flocculation rate, more nanosheets are curled to form regular nanotubes, thereby increasing the surface hydroxyl groups of the nanotubes and improving the adsorption capacity of ethyl mercaptan. The dynamic adsorption experiments show that the obtained H4Nb6O17 nanotubes present high ethyl mercaptan adsorption capacity and great cyclic regeneration performance. The high sulfur capacity of H4Nb6O17 nanotubes can be well explained by the abundant surface hydroxyl groups, large specific surface area and hierarchical pore structure. This work provided new insights into design and preparation of high-efficiency adsorbents by morphology and structure engineering.

Morphology Control in 2D Carbon Nitrides: Impact of Particle Size on Optoelectronic Properties and Photocatalysis

AbstractThe carbon nitride poly(heptazine imide), PHI, has recently emerged as a powerful 2D carbon nitride photocatalyst with intriguing charge storing ability. Yet, insights into how morphology, particle size, and defects influence its photophysical properties are virtually absent. Here, ultrasonication is used to systematically tune the particle size as well as concentration of surface functional groups and study their impact. Enhanced photocatalytic activity correlates with an optimal amount of those defects that create shallow trap states in the optical band gap, promoting charge percolation, as evidenced by time‐resolved photoluminescence spectroscopy, charge transport studies, and quantum‐chemical calculations. Excessive amounts of terminal defects can act as recombination centers and hence, decrease the photocatalytic activity for hydrogen evolution. Re‐agglomeration of small particles can, however, partially restore the photocatalytic activity. The type and amount of trap states at the surface can also influence the deposition of the co‐catalyst Pt, which is used in hydrogen evolution experiments. Optimized conditions entail improved Pt distribution, as well as enhanced wettability and colloidal stability. A description of the interplay between these effects is provided to obtain a holistic picture of the size–property–activity relationship in nanoparticulate PHI‐type carbon nitrides that can likely be generalized to related photocatalytic systems.

Mechanochemical synthesis of adsorbents based on silicon oxycarbide composites

In the work, an attempt was made to mechanochemically synthesize silicon oxycarbide composites from activated carbon and silica. Structure of the composites was studied using powder X-ray diffraction and IR spectroscopy. Formation of silicon oxycarbides was confirmed by presence of Si-O-C bond. Influence of the raw materials ratio on structural and chemical properties of resulting composites was revealed. With an increase of silica share in the initial mixture, a decrease in specific surface area and pore volume was noted, as well as an increase of the concentration of surface functional groups. Samples of the composites were tested in processes of sorption of methyl orange and fluoride ions. It was established that adsorption capacity for methyl orange decreased, while that for fluoride ions significantly increased comparing to activated carbon.

Influence of the Structure of a Surface Layer of Methyl Methacrylate-Based Cationic Particles on Adsorption of Biomolecules

Crosslinked cationic particles 200–600 nm in diameter have been synthesized via emulsifier-free copolymerization of methyl methacrylate and 2-aminoethyl methacrylate hydrochloride in the presence of cross-linking agents (N,N'-methylenebisacrylamide, triethylene glycol dimethacrylate, and diethylene glycol dimethacrylate). It has been shown that polymer particles with a maximum concentration of surface functional groups (1.42 µmol/m2) and a stable structure of a surface layer are formed only in the presence of ethanol (20 vol %). The synthesized particles efficiently adsorb biologically active substances, and their dispersions are stable against aggregation in buffer solutions at pH 7.0.

Characterization of biochars derived from various spent mushroom substrates and evaluation of their adsorption performance of Cu(II) ions from aqueous solution

A total of 16 biochar adsorbents were produced from four types of spent mushroom substrates to investigate the effect of pyrolysis temperature and raw material composition on the Cu(II) adsorption performance of the resulting biochars. It was determined that the pyrolysis temperature and substrate composition markedly influenced the thermal stability, the degree of carbonization, surface functional group content, and structural morphology of the biochars, but did not affect the adsorption isotherms or kinetics. Optimal results were obtained with an initial pH of 5, adsorbent dosage of 1 g/L, Cu(II) concentration of 50 mg/L, and temperature of 25 °C. The four best-performing biochars conformed to the Langmuir isotherm model and followed pseudo-second-order kinetics with maximum Cu(II) adsorption between 52.6 and 65.6 mg/g. Precipitation was the dominant mechanism for Cu(II) adsorption onto Lentinus edodes spent substrate-derived biochar pyrolyzed at 600 °C (LESS600), whereas complexation with surface functional groups was the prominent mechanism of Cu(II) removal by Auricularia auricula spent substrate-derived biochar pyrolyzed at 500 °C (AASS500). The Flammulina velutipes and Pleurotus ostreatus spent substrate-derived biochars pyrolyzed at 600 °C (FVSS600 and POSS600, respectively) removed Cu(II) ions using both precipitation and Cu2+−π complexation interactions. The findings indicate that biochar derived from spent mushroom substrates containing abundant lignin and pyrolyzed at high temperatures (500 or 600 °C) demonstrate effective Cu(II) removal because of the various physico-chemical properties discussed herein.

Physic-Mechanical Properties of Composites Based on Secondary Polypropylene and Dispersed of Plant Waste

The physic-mechanical properties of filled composites based on secondary polypropylene are investigated. As fillers the dispersed wastes of processing of agricultural plants - buckwheat and oat husk, as well as needles flour and wood flour were used. Water absorption, abrasion, impact strength and bending strength of composites were investigated. It has been proven that oat and buckwheat husks can be effectively used in composites based on secondary polypropylene and replace traditional wood fillers. It has been shown that the physic-chemical properties of the filled composites depend on the structure and physicochemical interactions on the phase separation surface, as well as on the surface properties of the filler particles. It is established that for the production of filled composites with improved physic-mechanical characteristics it is necessary to use fillers with small specific surface and concentration of surface functional groups, and the acid-base characteristic of the surface should be closer to neutral. It is shown that these conditions provide for the formation of a uniform structure of the filled composite with less internal stresses.

In Vitro Biological Impact of Nanocellulose Fibers on Human Gut Bacteria and Gastrointestinal Cells.

Wood-derived nanofibrillated cellulose (NFC) has long been recognized as a valuable nanomaterial for food-related applications. However, the safety of NFC cannot be predicted just from the chemical nature of cellulose, and there is a need to establish the effect of the nanofibers on the gastrointestinal tract, to reassure the safe use of NFC in food-related products. The present work selected the intestinal cells Caco-2 and the gut bacteria Escherichia coli and Lactobacillus reuteri to evaluate the in vitro biological response to NFC. NFC materials with different surface modifications (carboxymethylation, hydroxypropyltrimethylammonium substitution, phosphorylation and sulfoethylation) and unmodified NFC were investigated. The materials were characterized in terms of surface functional group content, fiber morphology, zeta potential and degree of crystallinity. The Caco-2 cell response to the materials was evaluated by assessing metabolic activity and cell membrane integrity. The effects of the NFC materials on the model bacteria were evaluated by measuring bacterial growth (optical density at 600 nm) and by determining colony forming units counts after NFC exposure. Results showed no sign of cytotoxicity in Caco-2 cells exposed to the NFC materials, and NFC surface functionalization did not impact the cell response. Interestingly, a bacteriostatic effect on E. coli was observed while the materials did not affect the growth of L. reuteri. The present findings are foreseen to contribute to increase the knowledge about the potential oral toxicity of NFC and, in turn, add to the development of safe NFC-based food products.