Iron Impregnation Research Articles

Removal of tetracycline from aqueous solution via Fenton process using iron-impregnated bamboo biochar

Abstract Tetracycline (TC) is a pharmaceutical that has been used extensively that its presence in water sources causes detriment to both aquatic life and human health. TC is not completely removed in wastewater treatment processes and could enter the environment through effluent and sludge. This study evaluated the potential of iron-impregnated bamboo biochar (Fe-biochar) as catalyst in the removal of tetracycline from aqueous solution via Fenton process. Characterization via Fourier transform infrared (FTIR) and energy dispersive X-ray spectroscopy (EDX) analyses verified the successful iron impregnation on biochar. TC removal was determined at 357nm absorbance through UV-Visible spectroscopy. Highest TC removal of 63.24% was achieved under conditions of 75 mg Fe-biochar, 0.45 M H2O2, and pH 5. Experimental data were assessed using the three factors Box-Behnken response surface experimental design where Fe-biochar dosage, H2O2 concentration, and solution pH were found to be significant parameters in TC removal. Furthermore, it was determined that the data fitted well in a reduced-cubic model with high coefficient of determination (R2 = 0.9990) which indicates good regression. The optimum conditions were found to be 39.44 mg Fe-biochar dosage, 0.05 M H2O2, and pH 4, with TC removal efficiency of 33.90%. Overall, the results of this study suggested that Fe-impregnated bamboo biochar can be used as an effective catalyst in removing tetracycline from aqueous solution via heterogeneous Fenton process.

Performance assessment of activated carbon thermally modified with iron in the desulfurization of biogas in a static batch system supported by headspace gas chromatography

A static batch arrangement composed of anti-leak vials coupled to gas chromatography is proposed as a complementary system for performance assessment of biogas desulfurization by adsorption. For testing, a modified commercial activated carbon produced by controlled thermal treatment in the presence of iron(III) species improved biogas desulfurization. The adsorbents showed a superior hydrogen sulfide removal compared to ordinary one. Pseudo-first-order, pseudo-second-order, and Bangham’s kinetic models were used to fit experimental data. All studied samples followed pseudo-first-order model, indicating the predominance of physisorption, and Bangham’s model, confirming that the micropores structure played an important role for gases diffusion and adsorbent capacity. Additionally, the materials were characterized by N2 adsorption–desorption, X-ray diffraction, infrared spectroscopy, scanning electron microscopy and energy-dispersive spectroscopy. The thermal treatment associated with iron impregnation caused significant modifications in the surface of the materials, and the iron species showed two main benefits: an expressive increase in the specific area and the formation of specific adsorption sites for hydrogen sulfide removal. The results reinforce the advantages of iron-modified adsorbents in relation to their non-modified counterparts. The analytical methodology based on the confinement of multiple gases contributes to improving the understanding of the hydrogen sulfide adsorption process using pressure swing adsorption technology.Graphical

Preparation of highly adsorptive biochar by sequential iron impregnation under refluxing and pyrolysis at low temperature for removal of tetracycline

Iron-doping modification is a prevailing approach for improving adsorption capability of biochar with environmental friendliness, but usually requires high temperature and suffers from iron aggregation. Herein, a highly adsorptive biochar was manufactured via sequential disperse impregnation of iron by refluxing and pyrolysis at low temperature for eliminating tetracycline (TC) from aqueous solution. Iron oxides and hydroxides were impregnated and stably dispersed on the carbon matrix as pyrolyzed at 200 °C, meanwhile abundant oxygen and nitrogen functional groups were generated on surface. The iron-doped biochar exhibited up to 891.37 mg/g adsorption capacity at pH 5, and could be recycled with high adsorption capability. The adsorption of TC should be mostly contributed to the hydrogen bonding of N/O functional groups and the hydrogen bonding/coordination of iron oxides/hydroxides. This would provide a valuable guide for dispersedly doping iron and conserving functional groups on biochar, and a super iron-doped biochar was prepared with superior recyclability.

Effect of iron impregnation ratio on the properties and adsorption of KOH activated biochar for removal of tetracycline and heavy metals

The effect of iron impregnation ratio on magnetic biochars (MBCs) prepared by biomass pyrolysis accompanied by KOH activation has been less reported. In this study, MBCs were produced by one-step pyrolysis/KOH-activation of walnut shell, rice husk and cornstalk with different impregnation ratios (0.3–0.6). The properties, adsorption capacity and cycling performance for Pb(II), Cd(II) and tetracycline of MBCs were determined. MBCs prepared with low impregnation ratio (0.3) showed stronger adsorption capacity on tetracycline. The adsorption capacity of WS-0.3 toward tetracycline was up to 405.01 mg g−1, while that of WS-0.6 was only 213.81 mg g−1. It is noteworthy that rice husk and cornstalk biochar with an impregnation ratio of 0.6 were more effective in removing Pb(II) and Cd(II), and the content of Fe0 crystals on surface strengthened the ion exchange and chemical precipitation. This work highlights that the impregnation ratio should be changed according to the actual application scenarios of MBC.

Simultaneous adsorption of Cd and As by a novel coal gasification slag based composite: Characterization and application in soil remediation

Cadmium (Cd) and arsenic (As) co-contamination has become increasingly serious in China agricultural soil due to rapid industrialization and urbanization. The opposite geochemical behaviors of Cd and As pose huge challenges for developing a material for their simultaneous immobilization in soils. Coal gasification slag (CGS) as a by-product of coal gasification process, is always dumped into a local landfill, which has a negative impact on environment. Few reports have been available on applying CGS as a material to immobilize simultaneously multiple soil heavy metals. A series of iron-modified coal gasification slag (IGS) composites IGS3/5/7/9/11 (with different pH values) were synthesized by alkali fusion and iron impregnation. After modification, carboxyl groups were activated, and Fe was successfully loaded onto the surface of IGS in the form of FeO and Fe2O3. The IGS7 exhibited the best adsorption capacity with the maximum Cd and As adsorption capacity of 42.72 mg/g and 35.29 mg/g, respectively. The Cd was mainly adsorbed through electrostatic attraction and precipitation, while the As through complexation with iron (hydr)oxides. IGS7 significantly reduced the bioavailability of Cd and As in soil with Cd bioavailability reduced from 1.17 mg/kg to 0.69 mg/kg and As bioavailability reduced from 10.59 mg/kg to 6.86 mg/kg at 1 % IGS7 addition. The Cd and As were all transformed to more stable fractions after IGS7 addition. The acid soluble and reducible Cd fractions were transformed into oxidizable and residual Cd fractions, and the non-specifically and specifically adsorbed As fractions were transformed to amorphous iron oxide-bound As fraction. This study provides valuable references for the application of CGS to the remediation of Cd and As co-contaminated soil.

Iron Nanoparticles to Catalyze Graphitization of Cellulose for Energy Storage Applications

The production of highly graphitic carbon from bioresources is an environmentally friendly approach to synthesize graphene for energy storage applications. Iron catalytic graphitization of cellulose, the most abundant biopolymer on earth, is an alternative approach as until now, cellulose has been classified as poorly graphitizable material. In this study, the impact of processing temperature and iron impregnation on the extent of graphitization of the cellulose-derived graphitic carbon nanostructure is uncovered by combining Raman spectroscopy, X-ray diffraction, transmission electron microscopy, and X-ray pair distribution function analysis. Raman spectroscopy is used in an innovative way to describe the evolution of the average graphitic phase size where the ash content misguides the X-ray diffraction analysis. A correlation was established between (i) the in-plane crystallite size La and the ID″/IG first-order ratio, (ii) the out-of-plane Lc crystallite size and the IG/Itot′ second-order ratio, and (iii) the second-order Raman IG′/Itot′ ratio and the average number of carbon layers per carbon crystallite. For iron-impregnated cellulose, phase quantification and analysis of the spatial distribution reveal highly crystalline rhombohedral graphite surrounded by a nanocrystalline carbon matrix. We explicitly show that traditionally non-graphitizable carbons can be used to form a graphite-like structure with multilayers of graphene sheets by careful addition of widely available nontoxic metal as catalysts. The study also shows that the impact of the catalyst is much more effective than the temperature in the nanostructure transformation. The proposed approach and the results obtained provide interesting insights that should stimulate further works aimed at extending the knowledge in the field.

Development of iron-based biochar for enhancing nitrate adsorption: Effects of specific surface area, electrostatic force, and functional groups

The problem of nitrate contamination in water has attracted widespread attention. Original biochar has a poor adsorption capacity for nitrate adsorption. Iron impregnation and acid protonation (base deprotonation) are common modification methods for biochar. In order to develop iron-mediated biochar containing multi-functional groups for enhancing nitrate adsorption, Fe-BC@H and Fe-BC@OH were prepared using a two-stage development process, including an iron-based carbon pyrolysis followed by acid protonation (or base deprotonation). The pseudo-second-order kinetic and Langmuir models can well describe the adsorption process which is a physicochemical complex monolayer adsorption. The data proved that Fe-BC@H (9.35 mg/g NO3−-N) had a stronger adsorption capacity than Fe-BC@OH (2.95 mg/g NO3−-N). Surface morphologies, functional groups, and mineral compositions of Fe-BC@H and Fe-BC@OH were analyzed through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Characterization results showed that acid protonation can further improve the specific surface area (SSA), pore volume, and Zeta potential of Fe-based biochar, providing more adsorption sites for nitrate and enhancing the electrostatic force between nitrate and biochar. However, these effects were suppressed through base deprotonation. In addition, acid protonation can significantly increase the type and number of functional groups of biochar to enhance the chemisorption of nitrate. Such results suggested that the acid protonation can further improve the adsorption capacity of Fe-based biochar for nitrate, while base deprotonation had an inhibitory effect on that of Fe-based biochar. Overall, this study reveals that specific surface area, electrostatic force, and functional groups are crucial effects of the nitrate adsorption on acid/base modified biochar.

ANN-GA based biosorption of As(III) from water through chemo-tailored and iron impregnated fungal biofilter system

The iron impregnated fungal bio-filter (IIFB) discs of luffa sponge containing Phanerochaete chrysosporium mycelia have been used for the removal of As(III) from water. Two different forms of same biomass viz. free fungal biomass (FFB) and modified free fungal biomass (chemically modified and iron impregnated; CFB and IIFB) have been simultaneously investigated to compare the performance of immobilization, chemo-tailoring and iron impregnation for remediation of As(III). IIFB showed highest uptake capacity and percentage removal of As(III), 1.32 mg/g and 92.4% respectively among FFB, CFB and IIFB. Further, the application of RSM and ANN-GA based mathematical model showed a substantial increase in removal i.e. 99.2% of As(III) was filtered out from water at optimised conditions i.e. biomass dose 0.72 g/L, pH 7.31, temperature 42 °C, and initial As(III) concentration 1.1 mg/L. Isotherm, kinetic and thermodynamic studies proved that the process followed monolayer sorption pattern in spontaneous and endothermic way through pseudo-second order kinetic pathway. Continuous mode of As(III) removal in IIFB packed bed bioreactor, revealed increased removal of As(III) from 76.40 to 88.23% with increased column height from 5 to 25 cm whereas the removal decreased from 88.23 to 69.45% while increasing flow rate from 1.66 to 8.30 mL/min. Moreover, the IIFB discs was regenerated by using 10% NaOH as eluting agent and evaluated for As(III) removal for four sorption–desorption cycles, showing slight decrease of their efficiency by 1–2%. SEM–EDX, pHzpc, and FTIR analysis, revealed the involvement of hydroxyl and amino surface groups following a non-electrostatic legend exchange sorption mechanism during removal of As(III).

Development of Iron fortified potato fries through Vacuum assisted processing strategies.

Potato fries, a relatively an untapped food matrix for fortification, was fortified with iron using vacuum impregnation technique and impact of this fortification on quality attributes (structure, color, texture, flavor, acrylamide, sensory characteristics) of the product was assessed. Further, to reduce the dietary restraints of consumers for fried fries, fat reduction was achieved using vacuum frying. Ferrous ammonium sulphate hexahydrate was used as a fortificant to yield 3.15mg iron from 30g fries (RACC for snacks- Recommended Amount Customarily Consumed). Effect of iron fortificant level, blanching, vacuum and restoration time (independent variable) were evaluated on responses (iron impregnation level and firmness) of fries using box-behnken design of response surface methodology. Results showed that blanching time was the most significant variable affecting iron impregnation followed by iron concentration and vacuum time. Ferrous ammonium sulphate hexahydrate was found to be the most appropriate fortificant since reflecting the least colour and sensory changes in fries. A fortified raw potato fries when fried under vacuum, provided better retention of colour and reduced fat absorption (by 17.72%) with comparable crispiness (0.37kg/sec vs 0.35kg/sec), firmness (0.39kg/sec vs 0.38kg/sec), color (ΔE = 1.39) and sensory score (7.9 vs 8.1 on 9-point scale) with control fries.

Machine learning exploration of the direct and indirect roles of Fe impregnation on Cr(VI) removal by engineered biochar

Data mining and knowledge discovery by machine learning (ML) have recently come into application in environmental remediation, especially the exploration for the multifactorial process such as hexavalent chromium [Cr(VI)] removal by iron-biochar composite (Fe-BC). The Cr(VI) removal capacity of Fe-BC was concurrently controlled by impregnated iron species (Fe0/Fe2+/Fe3+), carbon properties, and iron-carbon interactions, while the current lab-scale research could hardly untangle the overall relationships with the Cr(VI) removal experiments of one or several Fe-BCs under different research frameworks. Herein, we investigated the impacts of various microscopic material properties of Fe-BC on aqueous Cr(VI) removal by ML approach and highlighted the variations of biochar properties after iron impregnation. Our results suggested that the direct impacts of impregnated-iron contents on the Cr(VI) removal were limited, possibly related to undistinguished Fe species in the ML models, in which the roles of different iron species on Cr(VI) removal might be counteracted. Instead, the impacts of impregnated iron on the Cr(VI) removal were embodied indirectly by altering the biochar properties. Surface oxygen-containing functional groups (SOFGs) contents on biochar played a pivotal role in Cr(VI) removal according to the ML models. The condensed polyaromatic carbon matrices of BC and Fe-BC with a high content of non-polar carbon were also proved to be conducive to Cr(VI) removal. The ML models developed in this study consider surface functionalities information of BC and Fe-BC and offer a more accurate prediction for Cr(VI) removal, and the information mining behind models can act as a vital reference for the rational design of engineered biochar to remove aqueous Cr(VI).

Enhancing the adsorptive capacity of carbon nanofibers by impregnation with ferric oxide for the removal of cadmium from aqueous solution

Carbon nanofibers (CNF) possess remarkable surface properties and have been used in many applications, including water treatment. They are used for the removal of many contaminants from polluted water, including heavy metals. Further research is ongoing to enhance their removal efficiency for heavy metals. Previous studies involving the impregnation of metal oxides onto carbon adsorbents have reported an increase in CNF adsorption capacity. The incorporated ferric oxide, Fe2O3, can exist in different polymorphs. In this study, CNF impregnated with 10 wt% Fe2O3 nanoparticles was studied for its capacity to remove cadmium ions (Cd2+) from water. Both raw and Fe2O3-modified CNF (Fe-CNF) were characterized using several techniques. The SEM-EDX and XRF confirmed a successful impregnation of Fe2O3, while XRD, FTIR, and TGA showed that Fe2O3 was incorporated in the form of γ-Fe2O3 (a non-toxic and biodegradable polymorph). The effect of pH, contact time, temperature, and agitation speed on Cd2+ ions removal was tested in batch-mode adsorption experiments. The results revealed that Cd2+ ions removal efficiency achieved by Fe-CNF was around 80 % within 30 min of treating of 2.0 mg/L Cd solution at pH 8, adsorbent dosage of 5 g/L, and agitation speed of 150 rpm. The sorption of Cd2+ ions followed a pseudo-second-order model, and the thermodynamic studies indicated that iron impregnation changed the adsorption mechanism from a primarily endothermic process to a more efficient exothermic physical adsorption mechanism. Furthermore, the potential to regenerate and re-use the prepared Fe-CNF was established in 3 cycles of adsorption-desorption experiments. The 79 % cadmium recovery rate from Fe-CNF indicated its potential suitability for analytical purposes. The study demonstrated the advantage of impregnating CNF with ferric oxide to enhance the removal efficiency of Cd2+ ions from an aqueous solution.

Pre- and post-pyrolysis effects on iron impregnation of ultrasound pre-treated softwood biochar for potential catalysis applications

Slow pyrolysis is widely used to convert biomass into useable form of energy. Ultrasound pre-treatment assisted pyrolysis is a recently emerging methodology to improve the physicochemical properties of products derived. Biochar, the solid residues obtained from pyrolysis, is getting considerable attention because of its good physicochemical properties. Various modification techniques have been implemented on biochars to enhance their properties. Ultrasonic pre-treated wood biochar has showcased efficient surface and adsorption properties. Iron impregnated biochar is interesting as it has potentially proved the efficiency as an efficient low-cost catalyst. In this study, by combining the advantages of ultrasonic pre-treatment and iron impregnation, we have synthesized a series of Fe-impregnated biochar from softwood chips. Pre- and post-pyrolysis methods using a lab-scale pyrolyser had been implemented to compare the pyrolysis product yields and degree of impregnation. Biochars derived from ultrasound pre-treated woodchips by post pyrolysis demonstrated better impregnation of Fe ions on surface with better distribution of pyrolysis products such as biochar and biogas. The surface functionality of all ultrasound pre-treated biochars remained the same. However, post-pyrolysed samples at high frequency ultrasound pre-treatment showed better thermal stability. The chemical characteristics of these modified biochars are interesting and can indeed be used as a cost-effective replacement for various catalytic applications.

Superior fenton-like degradation of tetracycline by iron loaded graphitic carbon derived from microplastics: Synthesis, catalytic performance, and mechanism

Carbon-based catalyst (Fe-MPC) derived from microplastics was fabricated by facile iron impregnation and carbonization. Fenton-like degradation of tetracycline (TC) was investigated using Fe-MPC as catalyst. Effect of experimental factors, including H2O2 concentration, initial TC concentration, solution pH, temperature, anions, and natural organic matter, was examined to evaluate the catalytic performance. Under the conditions of Fe-MPC 0.02 g/L, H2O2 1.0 mM, pH 4.3, TC 40 mg/L, and temperature 25 °C, TC removal of above 83% is obtained within 10 min. The Fe-MPC catalyst displays superior catalytic performance to previous reports, as verified by the large rate constant (0.2571 min−1) and high specific TC removal (approximate 1500 mg/g catalyst). Fe-MPC catalyst was characterized by multi-techniques. Reduced iron species are uniformly distributed on graphitic carbon, and they act as active sites for H2O2 activation. The hydroxyl radicals are evidenced to be the dominant active radicals for Fenton-like degradation of TC by quenching experiments and electron spin resonance. Possible degradation pathways of TC are proposed based on the identified intermediates. This work brings a novel strategy of “waste treating waste” by the conversion of microplastics into Fenton-like catalyst for wastewater treatment.

Highly dispersed iron-doped biochar derived from sawdust for Fenton-like degradation of toxic dyes

Wastewater pollution is a global challenge in the field of environmental remediation. Functional biochar as Fenton-like catalyst receives growing attention for degradation of refractory organic contaminants in wastewater. This work provides a step-forward to develop effective functional biochar via revealing the mechanism of surface catalysis. The synthesis of iron-doped biochar (Fe@BC) was conducted through iron impregnation and carbonization of waste sawdust. Highly dispersed iron species on graphitic biochar is verified by multi-techniques including electron probe microanalyzer, transmission electron microscope, X-ray powder diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectrum and Raman spectrum. Rhodamine B (RhB) degradation above 92.7% is obtained within 140 min. Surface catalysis for generating hydroxyl radical is proved by iron determination, radical identification, and catalyst characterizations. Effective degradation of binary dyes is achieved. Fe@BC is an excellent catalyst with broad operation pH and highly stability. Promising application of the functional biochar provides a sustainable and ecofriendly strategy for wastewater treatment.

ZVI impregnation altered arsenic sorption by ordered mesoporous carbon in presence of Cr(Ⅵ): A mechanistic investigation

It is challenging to efficiently remove arsenate (As(Ⅴ)) and chromate (Cr(Ⅵ)) simultaneously. Herein, ordered mesoporous carbon (OMC) was fabricated with averaged pore diameter of 6.5 nm and surface area of 997 m2 g−1. Zerovalent iron (ZVI) impregnation reduced surface area of ZVI/OMC (432 m2 g−1) and increased ID/IG ratio by 13%. Maximal Cr(Ⅵ) and As(Ⅴ) sorption capacities at pH 3 were 0.66 and 0.019 mmol g−1 by OMC, and 0.71 and 0.39 mmol g−1 by ZVI/OMC, respectively. Reduction accounted for over 55% for Cr(Ⅵ) and As(Ⅴ) removal followed by complexation and precipitation. Better ZVI/OMC performance was ascribed to higher electron transfer rate and lower electrical resistance than OMC as per electrochemical analysis. Upon Cr(Ⅵ) introduction, As(Ⅴ) removal increased to 0.28 mmol g−1 by OMC, but decreased to 0.16 mmol g−1 by ZVI/OMC. OMC could preferably reduce CrO42− to Cr3+ by hydroxyl group, which enhanced its zeta potential facilitating As(Ⅴ) sorption. Regarding ZVI/OMC, Fe0 and Fe oxide in ZVI/OMC exhibited better affinity to As(Ⅴ), but the competition for the similar active sites resulted in compromised As(Ⅴ) and Cr(Ⅵ) removal. Thus, the novel OMC is advantageous for removal of binary As(Ⅴ) and Cr(Ⅵ), but ZVI/OMC is robust to detoxify single heavy metal.

Adsorption and regeneration on iron-activated biochar for removal of microcystin-LR

Novel iron activated biochars (FA-BCs) were prepared via simultaneous pyrolysis and activation of FeCl3-pretreated bermudagrass (BG) for removing microcystin-LR (MC-LR) in aqueous solution. Compared to the raw BC (without activation), the surface area and adsorption capacity of FA-BC at iron impregnation ratio of 2 (2 g FeCl3/g BG) were enhanced from 86 m2/g and 0.76 mg/g to 835 m2/g and 9.00 mg/g. Moreover, FA-BC possessed various iron oxides at its surface which provided the catalytic capacity for regeneration of MC-LR spent FA-BC and magnetic separation after the MC-LR adsorption. Possible mechanisms for the MC-LR adsorption onto FA-BC would include electrostatic attraction, π+-π, hydrogen bond, and hydrophobic interactions. The detailed adsorption studies indicated mainly chemisorption and intra-particle diffusion limitation would participate in the adsorption process. The thermal regeneration at 300 °C kept high regeneration efficiency (99–100%) for the MC-LR spent FA-BC during four cycles of adsorption-regeneration. In addition, the high regeneration efficiency (close to 100%) was also achieved by persulfate oxidation-driven regeneration. FA-BC also exhibited high adsorption capacity for the MC-LR from the real lake water to meet the MC-LR concentration below 1 μg/L as a safe guideline suggested by WHO.

Paper waste sludge-derived hydrochar modified by iron (III) chloride for enhancement of ammonium adsorption: An adsorption mechanism study

This work studied to use paper waste sludge for hydrochar production by hydrothermal carbonization with supporting NaOH solution at carbonization temperature of 200 °C for ammonium adsorption. The obtained original hydrochar was then modified with FeCl 3 to enhance the ammonium adsorption capacity. The batch adsorption experiments were conducted to test the effects of solution pH, contact time and initial ammonium concentration. The properties of original paper waste sludge hydrochar (OPSH) and iron modified paper waste sludge hydrochar (FPSH) were investigated using scanning electron microscopy (SEM, EDS), Powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results show that iron ions were successfully loaded on the OPSH with the most optimum adsorption capacity of ammonium at iron impregnation ratio of 10%(w/w). The results illustrate that the suitable conditions for ammonium adsorption were pH of 9, 120 min of contact time and an initial ammonium concentration of 80 mg/L. The highest adsorption capacities were 8.62 mg/g and 11.55 mg/g for OPSH and FPSH-10, respectively. The experimental data was fitted well by Langmuir, Sips models and the pseudo-second-order model with the R 2 of 0.9797 and 0.9946 (Langmuir model), 0.9926 and 0.9958 (Sips model) for OPSH and FPSH, respectively. In addition, the R 2 of the pseudo-second-order model were 0.9943 and 0.9881 for OPSH and FPSH, respectively. The adsorption process was controlled by monolayer chemisorption mechanism through cation exchange, surface complexation and electrostatic attraction. • The original hydrochar (OPSH) was fabricated from paper waste sludge. • The hydrochar (FPSH-10) was modified with FeCl 3 10% (w/w) for adsorption of 11.55 mg NH 4 \protect \relax \special {t4ht=＋} /g. • The NH 4 \protect \relax \special {t4ht=＋} adsorption kinetic was described the most exactly by the pseudo-second-order model. • The NH 4 \protect \relax \special {t4ht=＋} adsorption was controlled by cation exchange, electrostatic attraction and surface complexation.

Cotton fabric derived αFe magnetic porous carbon as electrocatalyst for alkaline direct ethanol fuel cell

Activate carbon (AC) demand has increased worldwide, with application in adsorption, heterogeneous catalysis, and most recently as electrocatalyst support. However, while AC production from agro-industrial waste are widely researched, textile waste is neglected as raw material. In this study, cotton fabric was first applied as textile dye adsorbent after iron impregnation, which enhanced the adsorption capacity. The dye adsorbed fabric was than sequentially pyrolyzed at 800 °C for 2 h under N2 atmosphere, producing a magnetic mesoporous activated carbon (MAC) of 472 m2 g-1 BET surface area with 82% micropores and magnetization saturation of 34.2 emu g-1 deriving from encapsulated metallic αFe. This new simple and fast one-step carbonization, activation and iron incorporation method, has very low chemicals consumption and waste generation compared to the traditionally applied ones. The so produced MAC was loaded with 20 % Pd and tested for electrocatalyst properties: high density current for ethanol oxidation of 549 mA mg-1Pd, 1.37 times higher than using commercial Pd catalyst, lower onset potential of -0.48 V vs NHE. Application of the electrocatalyst for direct ethanol fuel cell achieved a high energy production of 27 mW cm-2 at 353 K.

Iron-activated bermudagrass-derived biochar for adsorption of aqueous sulfamethoxazole: Effects of iron impregnation ratio on biochar properties, adsorption, and regeneration

This work focused on the impacts of FeCl3 impregnation ratio on the properties of FeCl3-activated bermudagrass (BG)-derived biochars (IA-BCs), adsorption of sulfamethoxazole (SMX) onto IA-BCs and regeneration of SMX-spent IA-BC. Compared with the control BC (85.82 m2/g), IA-BCs made via pyrolysis with FeCl3 to BG mass ratio between 1 and 3 (1–3 g FeCl3/g BG) resulted in significantly enhancing surface area (1014–1035 m2/g), hydrophobicity, Fe content in IA-BCs (3.87–7.27%), and graphitized carbon. The properties of IA-BCs supported magnetic separation and higher adsorption (32–265 mg SMX/g BC) than the control BC (6–14 mg SMX/g BC) at various pH. Adsorption experiments indicated various adsorption mechanisms between SMX and IA-BCs via π-π EDA, hydrophobic interactions, and hydrogen bond with intraparticle diffusion limitation. The adsorption was also found to be spontaneous and exothermic. The IA-BC made at FeCl3 to BG mass ratio of 2 (IA-BC2.0) showed the maximum adsorption capacity for SMX (253 mg SMX/g BC) calculated from Langmuir isotherm model. Additionally, both NaOH desorption and thermal oxidation showed effective regeneration of SMX-saturated IA-BC2.0 over multiple cycles. After three cycles of adsorption-regeneration, 64% and 62% of regeneration efficiencies were still achieved under thermal treatment at 300 °C and desorption with 0.1 M NaOH solution, respectively, indicating a cost-efficient adsorbent for the elimination of SMX in water.

Impact of pyrochar and hydrochar derived from digestate on the co-digestion of sewage sludge and swine manure

Four kinds of biochar were obtained by pyrolysis carbonization and hydrothermal carbonization from swine manure digestate, i.e. pyrochar (HC, HC-Fe) and hydrochar (HTC, HTC-Fe). Batch fermentation was conducted to compare their effects on the co-digestion of sewage sludge and swine manure. Both pyrochar and hydrochar present positive effect on methane production, nevertheless the higher methane yields were obtained in HTC and HTC-Fe digesters. No advantage was observed for the iron impregnation. The maximum methane yield was 308.4 mL/g VS in HTC digester, which was 27% and 49% higher than HC and Control, respectively. The surface functional groups of hydrochar are more abundant than pyrochar, which is favorable for promoting the syntrophic anaerobic metabolism, as revealed by the promoted substrate hydrolysis and VFAs consumption rate. Thus, it is proposed to convert swine manure digestate to hydrochar, which can be recirculated back to the AD reactor to increase the digestion efficiency.