Biochar Fibers Research Articles

Removal of 241Am from Aqueous Solutions by Adsorption on Sponge Gourd Biochar

Luffa cylindrica biomass was converted to biochar and the removal of 241Am by pristine and oxidized biochar fibers was investigated in laboratory and environmental water samples. This species has the added advantage of a unique microsponge structure that is beneficial for the production of porous adsorbents. The main purpose of this study was to valorize this biomass to produce an efficient adsorbent and investigate its performance in radionuclide-contaminated waters. Following the preparation of Am3+ solutions at a concentration of 10-12 mol/L, the adsorption efficiency (Kd) was determined as a function of pH, adsorbent mass, ionic strength, temperature, and type of aqueous solution by batch experiments. At the optimum adsorbent dose of 0.1 g and pH value of 4, a log10Kd value of 4.2 was achieved by the oxidized biochar sample. The effect of temperature and ionic strength indicated that adsorption is an endothermic and entropy-driven process (ΔH° = -512 kJ mol-1 and ΔS° = -1.2 J K-1 mol-1) leading to the formation of inner-sphere complexes. The adsorption kinetics were relatively slow (24 h equilibrium time) due to the slow diffusion of the radionuclide to the biochar surface and fitted well to the pseudo-first-order kinetic model. Oxidized biochar performed better compared to the unmodified sample and overall appears to be an efficient adsorbent for the treatment of 241Am-contaminated waters, even at ultra-trace concentrations.

Nitrogen sulfur dual-doped porous biochar fibers for high performance lithium-sulfur battery

Porous carbons have gained great attention for applications in lithium-sulfur (Li-S) batteries. However, achieving high specific surface area, hierarchical porosity, and abundant heteroatom-doping with facile approaches is still challenging. Herein, nitrogen, sulfur dual-doped hierarchical porous carbons (PBF@N@S) are obtained via a simple and sustainable activation process of cotton fibers. The as-prepared PBF@N@S exhibits a hierarchically interconnected network porous structure and large specific surface area. Meanwhile, abundant nitrogen, sulfur atoms are simultaneously doped in the carbons. These characteristics make the carbon favorable for hosting sulfur. The PBF@N@S sample with 50 wt% sulfur content (PBF@N@S-S-50%) delivers a high initial capacity with excellent cycling performance. Such high performance suggests that the PBF@N@S-S could be a promising cathode material for Li-S batteries.

Polonium removal from waters by silver-coated Luffa Cylindrica biochar fibers

Polonium removal from waters by silver-coated Luffa Cylindrica biochar fibers

Uranium Isotope (U-232) Removal from Waters by Biochar Fibers: An Adsorption Study in the Sub-Picomolar Concentration Range.

The adsorption of the U-232 radionuclide by biochar fibers in the sub-picomolar concentration range has been investigated in laboratory aqueous solutions and seawater samples. The adsorption efficiency (Kd values and % relative removal) of untreated and oxidized biochar samples towards U-232 has been investigated as a function of pH, adsorbent mass, ionic strength and temperature by means of batch-type experiments. According to the experimental data, the solution pH determines to a large degree the adsorption efficiency, and adsorbent mass and surface oxidation lead to significantly higher Kd values. The ionic strength and temperature effect indicate that the adsorption is based on the formation of inner-sphere complexes, and is an endothermic and entropy-driven process (ΔH° and ΔS° > 0), respectively. Regarding the sorption kinetics, the diffusion of U-232 from the solution to the biochar surface seems to be the rate-determining step. The application of biochar-based adsorbents to treat radioactively (U-232) contaminated waters reveals that these materials are very effective adsorbents, even in the sub-picomolar concentration range.

Ethylene-Vinyl Acetate (EVA) Containing Waste Hemp-Derived Biochar Fibers: Mechanical, Electrical, Thermal and Tribological Behavior.

To reduce the use of carbon components sourced from fossil fuels, hemp fibers were pyrolyzed and utilized as filler to prepare EVA-based composites for automotive applications. The mechanical, tribological, electrical (DC and AC) and thermal properties of EVA/fiber biochar (HFB) composites containing different amounts of fibers (ranging from 5 to 40 wt.%) have been thoroughly studied. The morphological analysis highlighted an uneven dispersion of the filler within the polymer matrix, with poor interfacial adhesion. The presence of biochar fibers did not affect the thermal behavior of EVA (no significant changes of Tm, Tc and Tg were observed), notwithstanding a slight increase in the crystallinity degree, especially for EVA/HFB 90/10 and 80/20. Conversely, biochar fibers enhanced the thermo-oxidative stability of the composites, which increased with increasing the biochar content. EVA/HFB composites showed higher stiffness and lower ductility than neat EVA. In addition, high concentrations of fiber biochar allowed achieving higher thermal conductivity and microwave electrical conductivity. In particular, EVA/HFB 60/40 showed a thermal conductivity higher than that of neat EVA (respectively, 0.40 vs. 0.33 W·m−1 ·K−1); the same composite exhibited an up to twenty-fold increased microwave conductivity. Finally, the combination of stiffness, enhanced thermal conductivity and intrinsic lubricating features of the filler resulted in excellent wear resistance and friction reduction in comparison with unfilled EVA.

Enhanced removal of As(III) by heterogeneous catalytic oxidation of As(III) on Fe-biochar fibers with H2O2 and hydroxylamine

Iron oxide-modified biochars are increasingly recognized as a promising arsenic adsorbent. However, most of them face serious challenges in the rapid and efficient removal of As(III). Herein, we integrated the iron oxide nanoneedles vertically covered biochar fibers (Fe-BFs) with H2O2 and Hydroxylamine (HA) to construct a heterogeneous catalytic system for the rapid oxidation and deep removal of As(III) from water. The system oxidized the As(III) to As(V) with high efficiency, and then the generated As(V) could be rapidly removed by adsorption onto Fe-BFs. The removal efficiency of As(III) by Fe-BFs/H2O2/HA at 120 min reached up to 98.93%, which is much higher than that of by Fe-BFs (69.20%) and Fe-BFs/H2O2 (92.32%). The system could work reliably in a wide pH range (4–10). Moreover, fixed-bed column experiments demonstrated that the addition of H2O2 and HA could increase the effective treatment volume from ~350 bed volume (BV) to ~700 BV to meet the drinking water standard (<10 μg/L). The introduction of HA induced the reduction of surface Fe(III) of Fe-BFs to surface Fe(II), which reacted with H2O2 to produce OH. The OH played a very important role in promoting the removal of As(III). This study offers a new strategy to enhance the applicability of Fe modified biochar for As(III) removal.

Adsorption of Hexavalent Chromium by Sodium Alginate Fiber Biochar Loaded with Lanthanum.

Lanthanun oxide (La2O3) is a lanthanum chemical compound incorporates a sensible anionic complexing ability; however, it lacks stability at a low pH scale. Biochar fibers will give the benefit of their massive space and plethoric uses on the surface to support a metal chemical compound. Herein, wet spinning technology was used to load La3+ onto sodium alginate fiber, and to convert La3+ into La2O3 through carbonization. The La2O3-modified biochar (La-BC) fiber was characterized by SEM, XRD and XPS, etc. An adsorption experiment proved that La-BC showed an excellent adsorption capacity for chromates, and its saturation adsorption capacity was about 104.9 mg/g. The information suggested that the adsorption was in step with both the Langmuir and Freundlich models, following pseudo-second-order surface assimilation mechanics, which showed that the Cr (VI) adsorption was characterized by single-phase and polyphase adsorption, mainly chemical adsorption. The thermodynamic parameters proved that the adsorption process was spontaneous and endothermic. The mechanistic investigation revealed that the mechanism of the adsorption of Cr (VI) by La-BC may include electrostatic interaction, ligand exchange, or complexation. Moreover, the co-existing anions and regeneration experiments proved that the La-BC is recyclable and has good prospects in the field of chrome-containing wastewater removal.

Copper Adsorption by Magnetized Pine-Needle Biochar

The Cu(II) adsorption from aqueous solutions by magnetic biochar obtained from pine needles has been studied by means of batch-type experiments. The biochar fibers have been magnetized prior (pncm: carbonized-magnetized pine needles) and after oxidation (pncom: carbonized-oxidized-magnetized pine needles) and have been used as adsorbents to study the presence of carboxylic moieties on the magnetization and following adsorption process. The effect of pH (2–10), initial metal concentration (10−5–9·10−3 mol·L−1) and contact time (0–60 min) has been studied by varying the respective parameter, and the adsorbents have been characterized by Fourier transform infrared (FTIR) and X-ray diffraction (XRD) measurements prior and after Cu(II)-adsorption. FTIR measurements were performed to investigate the formation of surface species and XRD measurements to record possible solid phase formation and characterize formed solids, including the evaluation of their average crystal size. The data obtained from the batch-type studies show that the oxidized magnetic biochar (pncom) presents significantly higher adsorption capacity (1.0 mmol g−1) compared to pncm (0.4 mmol g−1), which is ascribed to the synergistic effect of the carboxylic moieties present on the pncom surface, and the adsorption process follows the pseudo-second order kinetics. On the other hand, the FTIR spectra prove the formation of inner-sphere complexes and XRD diffractograms indicate Cu(II) solid phase formation at pH 6 and increased metal ion concentrations.

Efficient removal of arsenic from groundwater using iron oxide nanoneedle array-decorated biochar fibers with high Fe utilization and fast adsorption kinetics

Although Fe-based biochar adsorbents are attractive for removing arsenic from water due to their advantages of costing little and being producible at a large scale, the practical applications of these granular adsorbents are mainly limited by low Fe utilization and slow adsorption kinetics. In this study, iron oxide nanoneedle array-decorated biochar fibers (Fe-NN/BFs) adsorbents have been prepared through a simple hydrothermal reaction. The vertical growth of iron oxide nanoneedle arrays on the surface of biochar fibers maximizes Fe utilization and shortens As diffusion distance, thereby increasing As removal kinetics and capacity. Batch experiments show that the adsorption capacities of Fe-NN/BFs for As(V) and As(III) reach to 93.94 and 70.22 mg/g-Fe at pH 7.0, respectively. As(V) levels (275 μg/L) in groundwater are rapidly reduced (less than 5 min) to below 10 μg/L using Fe-NN/BFs (1 g/L) at pH 6.7. Similar As(III) levels can be reduced to below 10 μg/L within 30 min by Fe-NN/BFs (1.5 g/L). In fixed-bed experiments, the treatment volumes of As(V) and As(III) spiked groundwater reach to 2900 BV (26.2 L) and 2500 BV (22.6 L), respectively, using two columns packed with Fe-NN/BFs in tandem (C0 = 275 μg/L, 2 g of adsorbents in each column). When the As concentration in the influent is reduced to 50 μg/L (As(V): 25 μg/L + As(III): 25 μg/L), the treatment volume using one column reaches up to 11000 BV. The Fe-NN/BFs packed column can be easily regenerated and reused many times. After four regenerations, the treatment volume of As(V) and As(III) were reduced by 10.4% and 22.8%, respectively.

Evaluation of corrugated cardboard biochar as reinforcing fiber on properties, biodegradability and weatherability of wood-plastic composites

Corrugated cardboard (CCB) was pyrolyzed at different temperatures (350, 400 and 450 °C) to produce biochar fibers. The biochar and CCB control fibers were then compounded with high density polyethylene (HDPE) and maleated polyethylene (MAPE) to prepare wood plastic composites (WPC). The effect of different pyrolysis temperature biochars on the WPC's mechanical, thermal and viscoelastic properties, water absorptions, rheological behavior, weatherability and biodurability performance were evaluated. The CCB composite melts showed higher modulus and viscosity than biochar composites, indicating better melt strength. Compared with CCB composites, an increase of tensile strength (4%) and tensile modulus (30%) could be observed in composites made from CCB 350 °C biochar. In addition, the CCB biochar composite showed lower tan δ and adhesion factor, indicating the strong interfacial interaction between biochar fibers and HDPE. The composite melting temperatures (Tm) were not significantly different. The degree of HDPE crystallinity in the biochar composites decreased relative to the CCB composites, while the thermal properties of the composites improved compared with CCB composites. The CCB composite displayed the highest water absorption (3.9%) and thickness swell (3.8%) after 70 d. The CCB biochar (450 °C) composite experienced the least color change, lightless and carbonyl concentrations due to weathering. Pyrolysis of CCB reduced weight loss in the resulting composites exposed to fungi compared with the CCB composite. Using CCB biochar led to a more biodurable WPC.

Cu(II) adsorption on 2-thiouracil-modified Luffa cylindrica biochar fibres from artificial and real samples, and competition reactions with U(VI)

The adsorption of Cu(II) ions by biochar fibres prior and after modification with 2-thiouracil on real and artificial samples has been studied by batch-type adsorption experiments, FTIR and XPS spectroscopy and competition reactions using U(VI) ions as competitor cations. The experimental data of the artificial samples clearly show that the modified material presents extraordinary higher affinity for Cu(II) ions even in the acidic pH range, the spectroscopic data indicate the formation of inner-sphere complexes and the competition reactions significantly higher selectivity of the 2-thiouracil modified biochar fibres for Cu(II). The 2-thiouracil-modified biochar fibres have been successfully applied to acid mine drainage (AMD) samples regarding the selective separation of Cu(II) ions from “real” samples. Regarding the desorption of copper from the biochar surface, although 100% copper recovery was achieved by eluting the metal ion using 1 M HNO3, the deterioration of the modified biochar fibers due to extensive 2-thiouracil release from the biochar surface limits the applicability of the present adsorbent in routine and large-scale applications.

U(VI) adsorption by biochar fiber–MnO2 composites

The removal of U(VI) by biochar fibers from aqueous solutions has been investigated prior and after MnO2 surface-deposition. The removal efficiency has been studied as a function of pH, U(VI) concentration, ionic strength, temperature and contact time. The fibers morphology and surface complexes were analyzed by SEM–EDX and FTIR, respectively. Evaluation of the experimental data indicates that the composite presents extraordinary adsorption capacity (qmax = 3.8 mmol g−1, 904 mg g−1), which is attributed to the formation of inner-sphere surface complexes, and that the adsorption reaction is a relatively fast, endothermic and entropy-driven process.

Triggering selective uranium separation from aqueous solutions by using salophen-modified biochar fibers

Salophen modified biochar fibers derived from Luffa cylindrica sponges were prepared and subsequently studied as a potential U(VI) adsorbent by batch-type experiments. The material was characterized by spectroscopic and microscopic methods, which revealed no significant changes of the textural properties upon modification. The material presents extraordinarily high maximum adsorption capacity values (qmax) for U(VI) even under acidic conditions (714 g kg−1 at pH 3 and 833 g kg−1 at pH 5.5). This increased affinity is attributed to the selective binding of U(VI) by salophen and could be of particular interest for the adsorption of uranium from process solutions and industrial wastewaters.

Thorium adsorption by oxidized biochar fibres derived from Luffa cylindrica sponges

The present study deals with the preparation of oxidized biochar fibres derived from Luffa cylindrica sponges and the subsequent adsorption of Th(IV). The adsorption experiments were performed by batch-type experiments and include the effect of various physiochemical parameters, as well as characterization of the solid phases by means of spectroscopic (FTIR) and XRD measurements. The experimental data are best described by the pseudo-second order kinetic model (R2 = 0.998) and the adsorbent was found to have a relatively high adsorption capacity (qmax = 70 mg g−1) even at pH 3, attributed to the formation of inner-sphere complexes.

Surface characterization of oxidized biochar fibers derived from Luffa Cylindrica and lanthanide binding

In the last years, biochar fibers derived from Luffa Cylindrica have emerged as promising adsorbent material for harmful heavy metal ions. Based on their unique vascular structure, they exhibit a large surface area and thus high capability for the adsorption of metal ions. We investigated the structure and chemical surface composition of the carbonized fibers after treatment with 8M HNO3 prior and after Sm3+ binding in aqueous solutions. We used a large combination of classical analytical methods such as acid-base titration and batch-type adsorption experiments, as well as high-resolution microscopic and spectroscopic techniques like FTIR, XPS/REELS and SEM-EDX. The goal of the chemical oxidation is to functionalize the inner and outer surfaces of the biochar fibers by forming oxygen-containing active surface groups. Titration and spectroscopic data clearly reveal that anhydrides and carboxylic acids are acting as main surface groups to bind metal ions like Sm3+. We will show that the combination of high surface area and high density of carboxylic acid groups results in extremely high capacity of 2.4molkg−1 for the adsorption of Sm3+ ions. Therefore, the functionalization of biochar fibers offers a great potential to design advanced adsorbent materials for polluting heavy metal ions.

Copper Binding by Activated Biochar Fibres Derived from Luffa cylindrica

The adsorption of copper (Cu(II)) from aqueous solutions by activated Luffa cylindrica biochar fibres has been investigated by means of batch equilibrium experiments and FTIR spectroscopy. The effect of various physicochemical parameters, such as pH, initial metal concentration, ionic strength, mass of the adsorbent, contact time and temperature, has been evaluated by means of batch type adsorption experiments. FTIR spectroscopy, as well as acid-base titrations, was used for the characterization of the material and the surface species formed. According to the experimental results even at pH 3, the relative sorption is above 85% and the adsorption capacity of the activated biochar fibres for Cu(II) is q max = 248 g kg−1. Moreover, the interaction between the surface carboxylic moieties and Cu(II) results in the formation of very stable inner-sphere complexes (∆G o = −11.2 kJ mol−1 at pH 3 and −22.4 kJ mol−1 at pH 5.5).

Uranium binding by biochar fibres derived from Luffa cylindrica after controlled surface oxidation

Controlled surface modification of biochar fibres derived from Luffa cylindrica sponges has been carried out by nitric acid and the degree of oxidation could be controlled by changing the acid concentration or the reaction time. The extent of surface oxidation has been quantified by acid–base titration and FTIR-spectroscopy. Furthermore, uranium binding has been studied as a function of various parameters and the experimental results show that even under strong acidic conditions the relative sorption is above 80 % and the sorption capacity of the biochar fibres for U(VI) at pH 3 is qmax = 92 g kg−1.

Thorium removal from acidic aqueous solutions by activated biochar derived from cactus fibers

The removal of thorium from acidic aqueous solutions (pH 3) by activated biochar fibers obtained from Opuntia Ficus Indica has been investigated by batch experiments as a function of the initial metal concentration, ionic strength, temperature, and Fourier transform infrared spectroscopy. Activated biochar fibers demonstrated increased adsorption capacity for Th(IV) even in acidic solutions (qmax = 81 g kg−1), due to the formation of inner-sphere thorium complexes with the surface carboxylic moieties, indicating that the activated biochar fibers could be applied successfully for the removal of tetravalent metal ions from industrial process and wastewaters.

Removal of trivalent samarium from aqueous solutions by activated biochar derived from cactus fibres

AbstractThe efficiency of activated biochar fibres obtained from Opuntia Ficus Indica regarding the sorption of trivalent samarium (Sm(III)) from aqueous solutions was investigated by batch experiments. The effect of various physicochemical parameters (e.g. pH, initial metal concentration, ionic strength, temperature and contact time) on the Sm(III) adsorption was studied and the surface species were characterized by FTIR spectroscopy prior to and after the lanthanide sorption. The experimental results showed that the activated biochar fibres possessed extraordinary sorption capacity for Sm(III) in acidic solutions (qmax=90 g/kg, pH 3.0) and near neutral solutions (qmax=350 g/kg, pH 6.5). This was attributed to the formation of samarium complexes with the surface carboxylic moieties, available in high density on the lamellar structures of the bio-sorbent.

Uranium sorption from aqueous solutions by activated biochar fibres investigated by FTIR spectroscopy and batch experiments

The efficiency of activated biochar fibres obtained from Opuntia ficus indica regarding the sorption of hexavalent uranium (U(VI)) from aqueous solutions has been investigated by batch experiments, as a function of various physicochemical parameters, and FTIR spectroscopy prior and after U(VI) sorption. The experimental results show that the activated biochar fibres possess extraordinary sorption capacity for U(VI) even in acidic solutions (qmax = 210 g kg−1), which is attributed to the formation of inner-sphere complexes with the surface carboxylic moieties, available in high density on the lamellar structures of the bio-sorbent. The adsorption process is described by a two-step exothermic reaction.