Impregnation of biochar with montmorillonite and its activation for the removal of azithromycin from aqueous media.

An inexpensive and environmentally friendly composite synthesized from rice husk, impregnated with montmorillonite and activated by carbon dioxide, was investigated for the removal of azithromycin from an aqueous solution. Various techniques were used to characterize adsorbents in detail. The sorption process was primarily regulated by the solution pH, pollutant concentration, contact duration, adsorbent dose, and solution temperature. The equilibrium data were best analyzed using the nonlinear Langmuir and Sips (R2 > 0.97) isotherms, which revealed that adsorption occurs in a homogenous manner. The adsorption capacity of pristine biochar and carbon dioxide activated biochar-montmorillonite composite was 33.4 mg g-1 and 44.73 mg g-1, respectively. Kinetic studies identified that the experimental data obeyed the pseudo-second-order and Elovich models (R2 > 0.98) indicating the chemisorption nature of adsorbents. The thermodynamic parameters determined the endothermic and spontaneous nature of the reaction. The ion exchange, π-π electron-donor-acceptor (EDA) interactions, hydrogen-bonding, and electrostatic interactions were the plausible mechanisms responsible for the adsorption process. This study revealed that a carbon dioxide activated biochar-montmorillonite composite may be used as an effective, sustainable, and economical adsorbent for the removal of azithromycin from polluted water.

A feruloyl esterase/cellulase integrated biological system for high-efficiency and toxic-chemical free isolation of tobacco based cellulose nanofibers.

Tobacco based cellulose nanofiber (TCNF) is a novel nanocellulose that has recently been used to replace undesirable wood pulp fibers in the preparation of reconstructed tobacco sheets (RTS). However, given the strict requirements for controlling toxic chemical content in tobacco products, there is a global interest in developing a green, efficient, and toxic-chemical free approach to isolate TCNF from tobacco stem as a bioresource. In this study, we propose a creative and environmentally friendly method to efficiently and safely isolate TCNF from tobacco stem pulp, which involves integrated biological pretreatment followed by a facile mechanical defibrillation process. Feruloyl esterase is used to pretreat the stem pulp by disrupting the ether and ester bonds between lignin and polysaccharide carbohydrates within the fiber wall, which effectively facilitates cellulase hydrolysis and swelling of the stem pulp fiber, as well as the following mechanical shearing treatment for TCNF isolation. The results demonstrate that TCNF obtained by the comprehensive feruloyl esterase/cellulase/mechanical process exhibit uniform and well-dispersed nanofiber morphology, higher crystallinity, and stronger mechanical properties than those of the control. The addition of 0.5 % TCNF can replace wood pulp by 18 wt% ~ 25 wt% in the production of RTS samples while maintaining their reasonable strength properties.

Cellulose nanofibers as effective binders for activated biochar-derived high-performance supercapacitors.

Traditional hydrophobic binders can limit supercapacitors' performance by impeding ion accessibility. Herein, we demonstrate the potential of plant-derived environmentally friendly Cellulose Nanofibers (CNF) as binders for biochar (BN-Ac)-based supercapacitors. The CNF binder retains BN-Ac's micropores and improves wettability, while the Polyvinylidene Fluoride (PVDF) binder fills micropores and hinders ion-conductive pathways. The as-synthesized BN-Ac/CNF exhibits a capacitance of 268.4 F g-1 at 5 A g-1, which is 1.4 times higher than that of BN-Ac/PVDF. In addition, the energy density improves from 4.6 to 5.7 Wh kg-1 at 2.1 and 2.5 kW kg-1 power, respectively, for replacing PVDF with CNF. More importantly, BN-Ac/CNF shows outstanding capacitance retention of 96.2 % after 10,000 charge/discharge cycles. The improved wettability and reduced bulk electrolyte resistance by hydrophilic CNF binders are responsible for the electrode's high capacitance. Concurrently, this study showcases a facile strategy for improving supercapacitor performance and a green application of CNF in energy devices.

Strategies for arsenic pollution control from copper pyrometallurgy based on the study of arsenic sources, emission pathways and speciation characterization in copper flash smelting systems.

Arsenic in copper flash smelting (FS) systems not only affects the quality of products but also poses significant technological and environmental problems. Based on the assessment of arsenic mass partitioning in the FS system, arsenic elimination in off-gassing and tailings is 22%, and most of the arsenic output (69%) is recycled in the FS system. Circulating arsenic, especially arsenic in recycled dust and slag concentrate, is the key reason for high-arsenic-content feed. Dust-type recycled materials (RMs) contribute much more arsenic to the feed than slag-type RMs. Flash smelting furnace electrostatic precipitator (FSF ESP) dust contributes makese the largest contribution to arsenic among the dust-type RMs of mixed dust, especially trivalent arsenic, followed by FSF and flash converting furnace waste heat boiler (FCF WHB) dust, which contributes pentavalent arsenic. FCF WHB dust exhibits a relatively low arsenic content, consisting mainly of As(V)-O. Slag-type recycled materials contribute As(V)-O to the total feed, and As(III) originates from copper concentrates. Considering the arsenic contribution and environmental risk, reducing the recovery of FSF ESP dust can greatly decrease the arsenic grade of FSF feed and volatile As2O3. As one of the main arsenic sources in feed, FSF slag concentrate should be carefully disposed of if separated from feed materials because of its high arsenic-related environmental risk. In contrast, WHB dust and FCF slag are more suitable as RM due to their high copper content and low arsenic risk.

Preparation of N-doped biochar from sewage sludge and melamine for peroxymonosulfate activation: N-functionality and catalytic mechanisms.

In this study, a group of nitrogen-doped sludge biochar were prepared by a single-step pyrolysis method and employed as catalysts for the activation of peroxymonosulfate (PMS). The N content of as-synthesized biochar composites was altered by adding a different ratio of melamine with the precursors. The sample characterization results indicated that the N content of sludge-melamine-blended biochar named SM-(0.5:1) significantly increased from 1.91 to 9.93% compared with that of raw sludge biochar. Consequently, the surface area and mesoporosity also enhanced. SM-(0.5:1) exhibited excellent degradation ability of reluctant organic pollutants in PMS/acidic media, which outperformed many previously reported carbocatalysts. Complete color removal of a mixture solution of seven cationic and anionic dyes (10 mg L-1 of each) was achieved within 50 min by using 200 mg L-1 of SM-(0.5:1) and 350 mg L-1 of PMS. A mechanism study indicated that the non-radical process performed by the pyridine N dominated the oxidative degradation of pollutants rather than that of SO4- and OH radical process governed by graphitic N, CO, and surface metal oxides. This study concurrently provides a facile route of enhancing N functionality of sludge-based carbocatalysts and an efficient way of sludge valorization.

Contrasting effects of biochar and hydrothermally treated coal gangue on leachability, bioavailability, speciation and accumulation of heavy metals by rapeseed in copper mine tailings.

The purpose of this research was to examine the influence of hydrothermally treated coal gangue (HTCG) with and without biochar (BC) on the leaching, bioavailability, and redistribution of chemical fractions of heavy metals (HMs) in copper mine tailing (Cu-MT). An increase in pH, water holding capacity (WHC) and soil organic carbon (SOC) were observed due to the addition of BC in combination with raw coal gangue (RCG) and HTCG. A high Cu and other HMs concentration in pore water (PW) and amended Cu-MT were reduced by the combination of BC with RCG and/or HTCG, whereas individual application of RCG slightly increased the Cu, Cd, and Zn leaching and bioavailability, compared to the unamended Cu-MT. Sequential extractions results showed a reduction in the exchangeable fraction of Cu, Cd, Pb, and Zn and elevation in the residual fraction following the addition of BC-2% and BC-HTCG. However, individual application of RCG slightly increased the Cu, Cd, and Zn exchangeable fractions assessed by chemical extraction method. Rapeseed was grown for the following 45 days during which physiological parameters, metal uptake transfer rate (TR), bioconcentration factor (BCF), and translocation factor (TF) were measured after harvesting. In the case of plant biomass, no significant difference between applied amendments was observed for the fresh biomass (FBM) and dry biomass (DBM) of shoots and roots of rapeseed. However, BC-2% and BC-HTCG presented the lowest HMs uptake, TR, BCF (BCFroot and BCFshoot), and TF for Cu, Cd, Cr, Ni, Pb, and Zn in rapeseed among the other amendments compared to the unamended Cu-MT. Overall, these findings are indicative that using biochar in combination with RCG and/or HTCG led to a larger reduction in HMs leaching and bioavailability, due to their higher sorption capacity and could be a suitable remediation strategy for heavy metals in a Cu-MT.

Co-combustion of industrial coal slurry and sewage sludge: Thermochemical and emission behavior of heavy metals.

A combination of thermogravimetric analysis and lab-scale fixed bed combustion experiments was carried out to study the thermochemical, kinetic and heavy metals emission behavior during co-combustion of industrial coal slurry (CS) and sewage sludge (SS). The results found that the blends had integrative combustion profiles which reflected both coal slurry and sewage sludge. During co-combustion, the ignition performance of CS could be significantly improved with the addition of SS. Synergetic effects of the co-combustion were observed at lower temperature, while the high-temperature char combustion of the blends was inhibited because of high ash components of SS or formation of inactive alkali metal aluminosilicates. Kinetic analysis confirmed the improve iginition behavior of blends. Both the comprehensive combustibility index S and the activation energy suggested that the blends with 20% SS may have the best promoting effects. Compared with CS, the higher concentration of Cl in SS increased the volatilization ratios of Cu, Zn, As, and Pb. When added CS into SS, the volatilization ratios of arsenic decreased during combustion. The inhibition effects for arsenic during co-combustion might be associated with the capture of arsenic vapors by the new-formed Ca/Al from CS thermal decomposition.

Conversion of sewage sludge into environmental catalyst and microbial fuel cell electrode material: A review.

At present, environmentally friendly and cost-effective disposal of sewage sludge (SS) is the major challenge of wastewater treatment that prompted the concept of sludge valorization. A recent technology, SS conversion into biochar as an efficient catalyst for environmental application, shows great promise to sludge valorization. This review presents the literature and advances of sludge biochar-based catalysts (SBCs), including their synthesis route, physiochemical characteristics, catalytic applications, reaction mechanisms, chemical stability, feasibility, and future aspects. Two major applications of SBCs such as organic pollutants degradation and employing as an electrode material in a microbial fuel cell (MFC) were summarized. The literature has indicated that carbonization of raw or organic/ inorganic-laden sludge produces various metal phase structure and surface functional groups which perform various catalytic reaction such as Fenton-like reaction, ozonation, H2O2/ persulfate activation, and photoreaction in the organic pollutants degradation tests. The degradation efficiency and chemical stability of SBCs have found very satisfying. Moreover, catalysts are highly recyclable, separable, and ensure negligible metal leaching. Secondly, high-temperature carbonized sludge exhibits excellent electrical conductivity which is suitable to use as MFC electrodes. The low-cost sludge biochar-based electrodes (SBEs) performance is comparable to many commercial electrodes. This new technology is concurrently advantageous for environmental pollution remediation, energy production, and harmful metals immobilization, which offer a new route towards SS valorization.

One-step synthesis of N-doped metal/biochar composite using NH3-ambiance pyrolysis for efficient degradation and mineralization of Methylene Blue.

A series of new biochar-supported composite based on the combination of biochar and metallic nanoparticles (NPs) were produced through single-step pyrolysis of FeCl3-Ti(OBu)4 laden agar biomass under NH3 environment. The physiochemical properties of composites were characterized thoroughly. It has found that heating temperature and N-doping through NH3-ambiance pyrolysis significantly influence the visible-light sensitivity and bandgap energy of composites. The catalytic activities of composites were measured by degradation of Methylene Blue (MB) in the presence or absence of H2O2 and visible-light irradiation. Our best catalyst (N-TiO2-Fe3O4-biochar) exhibits rapid and high MB removal competency (99.99%) via synergism of adsorption, photodegradation, and Fenton-like reaction. Continuous production of O2- and OH radicles performs MB degradation and mineralization, confirmed by scavenging experiments and degradation product analysis. The local trap state Ti3+, Fe3O4, and N-carbon of the catalyst acted as active sites. It has suggested that the Ti3+ and N-doped dense carbon layer improve charge separation and shuttle that prolonged photo-Fenton like reaction. Moreover, the catalyst is highly stable, collectible, and recyclable up to 5 cycles with high MB degradation efficiency. This work provides a new insight into the synthesis of highly visible-light sensitized biochar-supported photocatalyst through NH3-ambiance pyrolysis of NPs-laden biomass.

Sewage sludge-derived TiO2/Fe/Fe3C-biochar composite as an efficient heterogeneous catalyst for degradation of methylene blue.

Novel TiO2/Fe/Fe3C-biochar composite, as a heterogeneous catalyst, has been synthesized by a single-step route, where sewage sludge (SS) and different ratios of nanoparticles (NPs: Fe and Ti) impregnated with chitosan using coagulation and flocculation techniques for subsequent thermal decomposition at 800 °C. The physiochemical properties of samples have been characterized thoroughly and employed in methylene blue (MB) degradation tests. It was found that NPs ratio and chitosan support have significant influences on the properties and catalytic activity of catalysts. Chitosan inclusion successfully improves the surface area and mesoporosity of composites, while high contents of Fe integration reduce surface area and active site (Fe3C) due to Fe0 agglomeration. Though, Ti incorporation produces Ti3+ that activated photosensitivity. Catalyst with the high mesoporous surface, Ti3+, selective Fe3C, and small Fe0 shows superior MB removal competency through concurrent adsorption, photodegradation, and H2O2 activation. Primarily OH and some O2- radicles participating in the degradation reactions evident from scavenging experiments. The maximum MB removal capacity evaluated as 376.9 mg L-1 in neutral pH. Moreover, the catalyst exhibits excellent material stability, recyclability, easy separability, and low Fe-ion leaching (0.11 mg L-1) after catalysis. This study provided new insight into a low-cost and environmentally friendly route of catalyst synthesis using SS, NPs, and chitosan, which concurrently advantageous to SS disposal and wastewater treatment.

Emission and transformation behavior of minerals and hazardous trace elements (HTEs) during coal combustion in a circulating fluidized bed boiler.

Emission of hazardous trace elements (HTEs) from energy production is receiving much attention due to concerns about the toxicity to the ecosystem and human health. This study presented new field measurement data on the HTEs partitioning behavior and size-segregated elemental compositions of gaseous particular matter (PM) generated from a commercial circulating fluidized bed (CFB) power plant. Mineralogical and morphological characteristics of combustion ash and PM2.5 (particle diameter less than 2.5 µm) were determined by X-ray diffractometer (XRD) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDS). Functional groups alteration during CFB combustion was characterized by Fourier transform infrared spectroscopy (FTIR). The presence of aliphatic hydrogen at 2910 cm-1 and 2847 cm-1 in the PM2.5 suggested that the aliphatic carbon-rich volatiles were absorbed on the fine particles with large surface area. Fine fly ash (PM2.5) occurred as irregular glass particles or/and as unburned carbon. The typical irregular particles were mainly composed of Al-Si-Ca or Al-Si-Fe phases. The enrichment behavior of HTEs was determined for the airborne size-segregated particular matter. Elemental occurrences, combustion temperature, unburnt carbon, and limestone additives during CFB combustion were critical in the transformation behavior of HTEs. The total potentially mobile pollutants that exit the CFB power plant every year were estimated as follows: 0.22 tons of Cr, 0.12 tons of Co, 0.73 tons of Ni, 0.04 tons of As, 0.07 tons of Se, 3.95 kg of Cd, and 3.34 kg of Sb.

Simultaneous functionalization and magnetization of biochar via NH3 ambiance pyrolysis for efficient removal of Cr (VI).

Enhancing biochar adsorption capabilities and recollection ability is essential for efficient biochar application. In this study, Nitrogen-doped magnetic biochar was prepared via one-step heating of FeCl3-laden agar biomass under NH3 environment. Synthesized magnetic biochar ABF-N800 shows a maximum Cr (VI) adsorption capacity up to 142.86 mg g-1, outperforming that of magnetic biochar and many other previously reported materials. Moreover, a significant increase of magnetic properties obtained by NH3 ambiance pyrolysis enables easy separation of the adsorbent from the solution after treated with Cr (VI). The physiochemical properties of composites characterized by SEM, EDS, XRD, XPS, VSM, BET surface and pore, Elemental content, and FTIR analysis. The NH3 ambiance pyrolysis confirmed as an efficient process for surface modification, increased magnetic properties and activated N-functional groups. The Langmuir isotherm model and pseudo-second-order model are applicable for describing adsorption behavior. The thermodynamic study shows that the adsorption was spontaneous and endothermic. The present results warrant the application of simultaneous functionalized and magnetized biochar for Cr (VI) contaminated wastewater treatment.

Recent progress in biochar-supported photocatalysts: synthesis, role of biochar, and applications.

Incorporating photocatalytic nanoparticles with biochar templates can produce biochar-supported photocatalysts (BSPs) and combine the advantages of biochar with catalytic nanoparticles. The obtained composite exhibits excellent surface properties, crystallinity, chemical stability, recoverability, and higher photocatalytic competency than the bare semiconductor photocatalyst. The literature and advances in BSPs based on the combination of low-cost biochar and catalytic nanoparticles are presented in this review. Various synthetic techniques and physicochemical properties of BSPs are summarized. The article then discusses in detail the important role of biochar in influencing the photocatalytic performance of BSPs such as supporting nanoparticles, increasing the surface area and the number of active sites, shuttling electrons, acting as an electron reservoir, increasing charge separation, and reducing band gap energy. Furthermore, the synergistic effects of adsorption and photodegradation of organic pollutants by BSPs are discussed with in-depth mechanistic evidence. Finally, the application of BSPs in various fields and constructive suggestions for their future development are reported.

Developmental selenium exposure and health risk in daily foodstuffs: A systematic review and meta-analysis.

Selenium (Se) is a trace mineral and an essential nutrient of vital importance to human health in trace amounts. It acts as an antioxidant in both humans and animals, immunomodulator and also involved in the control of specific endocrine pathways. The aim of this work is to provide a brief knowledge on selenium content in daily used various foodstuffs, nutritional requirement and its various health consequences. In general, fruits and vegetables contain low content of selenium, with some exceptions. Selenium level in meat, eggs, poultry and seafood is usually high. For most countries, cereals, legumes, and derivatives are the major donors to the dietary selenium intake. Low level of selenium has been related with higher mortality risk, dysfunction of an immune system, and mental failure. Selenium supplementation or higher selenium content has antiviral outcomes and is necessary for effective reproduction of male and female, also decreases the threat of chronic disease (autoimmune thyroid). Generally, some advantages of higher content of selenium have been shown in various potential studies regarding lung, colorectal, prostate and bladder cancers risk, nevertheless results depicted from different trials have been diverse, which perhaps indicates the evidence that supplementation will merely grant advantage if the intakes of a nutrient is deficient. In conclusion, the over-all people should be advised against the usage of Se supplements for prevention of cardiovascular, hepatopathies, or cancer diseases, as advantages of Se supplements are still ambiguous, and their haphazard usage could result in an increased Se toxicity risk. The associations among Se intake/status and health, or disease risk, are complicated and need exposition to notify medical practice, to improve dietary recommendations, and to develop adequate communal health guidelines.

Enhanced removal of hexavalent chromium from aqueous media using a highly stable and magnetically separable rosin-biochar-coated TiO2@C nanocomposite.

Recently, nanosized metal-oxides have been extensively investigated for their ability to remove metal ions from aqueous media. However, the activity and capacity of these nanosized metal-oxides for removing metal ions decrease owing to their agglomeration in aqueous media. Herein, we synthesized a highly stable and magnetically separable rosin-biochar-coated (RBC) TiO2@C nanocomposite through a facile and environment-friendly wet chemical coating process, followed by a one-step heating route (pyrolysis) for efficient removal of Cr(vi) from aqueous solution. An array of techniques, namely, TEM, HRTEM, TEM-EDS, XRD, FTIR, VSM, BET and TGA, were used to characterize the prepared nanocomposite. The pyrolysis of rosin into biochar and the fabrication of Fe onto the RBC-TiO2@C nanocomposite were confirmed by FTIR and XRD examination, respectively. Moreover, TEM and HRTEM images and elemental mapping using TEM-EDS showed good dispersion of iron and carbon on the surface of the RBC-TiO2@C nanocomposite. Sorption of Cr(vi) ions on the surface of the RBC-TiO2@C nanocomposite was very fast and efficient, having a removal efficiency of ∼95% within the 1st minute of reaction. Furthermore, thermodynamic analysis showed negative values of Gibb's free energy at all five temperatures, indicating that the adsorption of Cr(vi) ions on the RBC-TiO2@C nanocomposite was favorable and spontaneous. Conclusively, our results indicate that the RBC-TiO2@C nanocomposite can be used for efficient removal of Cr(vi) from aqueous media due to its novel synthesis and extraordinary adsorption efficacy during a short time period.