Excellent Removal Capacity Research Articles

Performance of single PN/A reactor under wide fluctuation of nitrogen load.

Partial nitritation-anammox (PN/A) is a cost-effective technology in high ammonia-nitrogen wastewater treatment. However, PN/A is prone to instability as the ammonia-nitrogen sharply fluctuates. In this study, a packed bed reactor is employed to construct a single-stage PN/A system to investigate the operational characteristics and explore the denitrification mechanism. The effluent NH4+-N concentration, ammonia nitrogen removal rate (ARE), and total nitrogen removal rate (TNR) could be sustained at about 60mg/L, 80%, and over 70%, respectively, when the influent nitrogen load rate (NLR) is changed from 0.733 to 0.879kg-N/m3/day. Both ARE and TNR are decreased when NLR continues increasing to 1.026kg-N/m3/day. The influent NLR decreases from 0.879 to 0.147kg-N/m3/day, and ARE and TNR reached 98% and 85.4%, respectively. Therefore, the denitrification effect of the reactor could be recovered, and the excellent nitrogen removal capacity could be obtained within a wide range of influent NLR. Moreover, the high-throughput sequencing and metagenomic testing indicate that the Proteobacteria and Planctomycetes that the PN/A functional strains (i.e., ammonia-oxidizing bacteria (AOB) and anammox bacteria (AnAOB)) account for 38.8% in the sludge. The relative abundance of Nitrospira containing the nitrite-oxidizing bacteria (NOB) has dropped to 0.01%, and the functional gene nxr of the nitrite oxidation process is also inhibited. The relative expression of the functional gene is dominated by the short-range nitritation and anammox oxidation, which demonstrates that the nitrogen removal is mainly dominated by nitritation-anammox.

Synergistic effect of CaCO3 particles and porous carbon towards the removal of Zn2+ ions in aqueous solutions

This work describes the preparation of an adsorbent containing CaCO3 particles dispersed in activated carbon and its use for the removal of Zn2+ ions from aqueous solutions. The combination of the large porosity of the activated carbon support with the easy ion exchange occurring at the surface of the carbonate particles led to the achievement of fast adsorption kinetics and excellent ion removal capacity for the composite adsorbent. The material was synthesized by wet impregnation of the porous carbon support with an aqueous solution of Ca(NO3)2, followed by evaporation of the solvent with subsequent heat treatment in an inert atmosphere. X-ray diffraction results demonstrated the presence of CaCO3 crystals in the material, but with broad and low intensity diffraction peaks, corresponding to an average crystallite size of 20 nm; solid-state 13C NMR spectroscopy confirmed the presence of this phase by means of the identification of the signal relative to the 13C nuclei of the CO32− group at ∼170 ppm. The carbon-based adsorbent containing the CaCO3 particles showed excellent ability to remove Zn2+ ions from aqueous solutions, with essentially all ions removed after 30 min of contact time. In addition, the kinetic analysis data were properly fitted using the pseudo-second order model, pointing to the occurrence of chemisorption as the rate limiting of the process. The equilibrium adsorption isotherms were correctly described by the Langmuir model, indicating that the adsorption takes place with the formation of a monolayer on the adsorbent surface. The results evidenced a synergistic effect of the porous carbon and the CaCO3 particles regarding the Zn2+ ions removal, with a fast adsorption kinetics at the initial stage of adsorption attributed to the high availability of the dispersed CaCO3 particles on the carbon surface.

Highly efficient removal of Pb2+ and Cd2+ on MgAl-LDH modified with carbon dots, citric acid and amino silane: Kinetic, isothermal and mechanistic studies

To increase active sites for Pb2+ and Cd2+ removal, MgAl-layered double hydroxide (MgAl-LDH) was modified with carbon dots (CDs), citric acid (CA) and 3-triethoxysilylpropylamine (APTES) via a step-by-step hydrothermal method. The resultant composite (LCC-NH2) exhibited excellent removal capacity of 511.5 mg/g and 166.0 mg/g for Pb2+ and Cd2+ at 298 K, which were 6-fold and 12-fold that of MgAl-LDH. Pb2+ and Cd2+ removal fits best to the pseudo-second-order kinetic and Langmuir isotherm models. And thermodynamic studies indicated the adsorption of Pb2+ and Cd2+ on LCC-NH2 was spontaneous. In a multifaceted metal system, LCC-NH2 still demonstrated superior removal capacity for Pb2+ and Cd2+. However, it showed greater selectivity for Pb2+ than Cd2+. The mechanism studies indicated the efficient removal of Pb2+ and Cd2+ was mainly attributed to the synergistic effect encompassing isomeric substitution, chelation, and precipitation. Therefore, LCC-NH2 offers considerable potential for practical applications in environmental remediation efforts.

Catalytic fixation of hydrogen sulfide over CuO-CaCO3 co-impregnated tea stalk-derived biochar

Effective treatment of hydrogen sulfide (H2S) is crucial for minimizing nuisance odors from intensive livestock and poultry operations. The development of high-performance desulfurizers holds practical significance in this context. Herein, a novel CuO-CaCO3 co-impregnated biochar desulfurizer (CuxCay/BCT) was synthesized by impregnation-pyrolysis method, using waste tea stalks and metal salts as raw materials, and it is intended for the treatment of H2S at room temperature. The optimized Cu0.75Ca0.25/BC800 shows an excellent H2S removal capacity of 182.67 mg/g, which is 31 times and 5.6 times that of inactivated biochar (BC800) and copper-oxide-impregnated biochar (Cu0.75/BC800). The desulfurization mechanism of Cu0.75Ca0.25/BC800 involves synergistic effect of reactive adsorption and catalytic oxidation. CaCO3’s alkaline adsorption sites and copper-mediated activation of superoxide radicals (∙O2-) were critical in this reaction. Besides, Cu0.75Ca0.25/BC800 demonstrated excellent reusability, retaining approximately 85 % of its initial H2S removal capacity after seven cycles of desulfurization and regeneration. This study aims to develop a metal oxide- and carbonate-impregnated biochar-based desulfurizer, with the goal of advancing the technology for catalytic removal of H2S in a more environmentally friendly and effective manner.

A comparative study of algal-bacterial granular sludges and aerobic granular sludge at different C/N ratio: Granule characteristics, SND progress and Microbial community

The algal-bacterial synergistic effect in algal-bacterial granular sludge (ABGS) made its nitrogen metabolism mechanism different from that of aerobic granular sludge (AGS). In this study, the effects of algae on granules characteristics, SND process and community structure in ABGS were studied by treating wastewater with different C/N (13:1–20:1) ratios. The results showed that ABGS and AGS had excellent nitrogen removal capacity of 86 % and 91 %, respectively, and SND efficiency was above 90 %. ABGS granules were looser due to the phototaxis of algae, and the oxygen penetration depth was higher than that of AGS. The NH4+-N removal efficiency of AGS was higher than that of ABGS, but the SND efficiency of ABGS was better than that of AGS. In ABGS, photosynthesis provided organic carbon for denitrification in anaerobic period, and organic carbon might be more important than strict anaerobic environment. In aerobic period, The SND process in ABGS was mainly heterotrophic nitrification aerobic denitrification (HAND), while in AGS was conventional simultaneous nitrification denitrification (CSND). The results of this study would provide a theoretical foundation for further understanding the difference between ABGS and AGS nitrogen removal mechanisms and help to further expand the application of ABGS in practical engineering.

Recyclable chitosan adsorbent: Facile functionalization strategy, excellent removal capacity of dyes and adsorption mechanism

The development of chitosan-based adsorbents with facile preparation, high adsorption performance and reusability for the removal of contaminant dyes remains a persistent challenge. To overcome this challenge, herein, we have developed a novel and extremely facile one-step strategy by which a new high-performance chitosan/polyethyleneimine/polyethylene glycol diglycidyl ether adsorbent (named as CC/PEI/PGDE) has been successfully fabricated via direct functionalization of CC by PEI at ambient temperature followed by subsequent freeze-drying. The Box-Behnken Design was employed to optimize the concentrations of adsorbent components. Attractively, this adsorbent exhibit outstanding adsorption performances to congo red (RED), acid blue-25 (BLUE) and amino black-10B (BLACK) with 2901 mg g−1 (90.9 %), 3434 mg g−1 (90.9 %), and 1438 mg g−1 (90.1 %) of adsorption capacities (removal efficiencies), respectively, and maintains nearly the same adsorption behaviors to original adsorbent even after 6 cycles of adsorption-desorption processes. Meanwhile, three kinetic models, three isothermal models, and the Vant Hoff model are employed to further investigate the adsorption behaviors of RED, BLUE, and BLACK dyes by CC/PEI/PGDE. The results from SEM, EDS, BET, FT-IR, pHZPC and XPS confirm that hydrogen bond interactions and electrostatic attractions play crucial roles in facilitating dyes adsorption by CC/PEI/PGDE. It is expected that this work can bring forward a new perspective for the facile design of high-performance adsorbent for removing anionic dyes from wastewater.

Bifunctional nanocomposites formed from magnetic lignin-derived carbon and molybdenum disulfide for efficient pollutant removal

The development of inexpensive and robust bifunctional nanocomposites toward efficient pollutant removal is crucial for wastewater remediation. Herein, we report a novel strategy for fabrication of magnetic nanocomposites loaded with molybdenum disulfide (Fe3O4/PLC-MoS2) using lignin biomacromolecules for efficient pollutant removal. The Fe3O4/PLC-MoS2 exhibit excellent pollutant removal capacity: The adsorption capacity of Pb(II) achieve 236.1 mg/g and the methylene blue (MB) degradation rate is up to 90.0 % within 20 min. The adsorption mechanism reveal that the enhanced removal properties is due to that the S atoms on the loaded MoS2 could convert into soluble sulfide and react with Pb(II) to form white precipitate β-Pb3O2SO4. Moreover, the experiments results demonstrate that the Fe3O4/PLC-MoS2 has a low bandgap, which can activate PMS to produce reactive oxygen species and degrade MB molecules efficiently. Notably, the Fe3O4/PLC-MoS2 demonstrate continued outstanding wastewater remediation capabilities even in scenarios where Pb(II) and MB coexisted. Overall, this study offers a viable and eco-friendly design of dual function removal material by using lignin waste toward promising implications for wastewater treatment.

Zeolitic imidazolate framework derived Fe catalyst electrocatalytic-driven atomic hydrogen for efficient reduction of nitrate to N2

Excessive discharge of nitrogen-containing chemical products into the natural water environment leads to the serious environmental problem of nitrate-nitrogen pollution, threatening the ecological balance and human health. In this study, we propose an efficient denitrification electrochemical method utilizing iron-doped zeolite imidazolium framework derived defective nitrogen-doped carbon (d-FeNC) catalysts. The d-FeNC catalyst exhibited 97 % nitrate removal efficiency and 94 % total nitrogen (TN) removal, and the reaction rate constant was increased from 0.73 h−1 of the Fe-undoped electrocatalyst (d-NC) to 1.11 h−1. The successful synthesis of d-FeNC with carbon defect sites and encapsulated Fe was confirmed by in-depth characterization. In situ electron paramagnetic resonance (EPR) analysis in conjunction with cyclic voltammetry (CV) tests confirmed the carbon substrates with defect enhanced the trapping of atomic hydrogen (H*) on the catalyst surface. Density functional theory (DFT) calculations clarified the doping of Fe facilitated the adsorption of nitrate, resulting in contact of H* with nitrate on the catalyst surface. In the synergy of the defective state organic framework and metal Fe, H* and nitrate realized a collision process. The electrochemical denitrification system achieved an excellent nitrate removal capacity of 7587 mgN·g−1cat in high-concentration nitrate solution and showed excellent stability under various conditions. Overall, this study underscores the potential of defective iron-doped carbon catalysts for efficient electrocatalytic denitrification, providing a promising approach for sustainable wastewater treatment.

High performance self-assembled sulfidized nanoscale zero-valent iron for the immobilization of cadmium in contaminated sediments: Optimization, microbial response, and mechanisms

Sulfidized nanoscale zero-valent iron (S-nZVI) showed excellent removal capacity for cadmium (Cd) in aqueous phase. However, the remediation effects of S-nZVI on Cd-contaminated sediment and its interactions with microorganisms in relation to Cd fate remain unclear. The complexity of the external environment posed a challenge for Cd remediation. This study synthesized S-nZVI with different S and Fe precursors to investigate the effect of precursors and applied the optimal material to immobilize Cd in sediments. Characterization analysis revealed that the precursor affected the morphology, Fe0 crystallinity, and the degree of oxidation of the material. Incubation experiments demonstrated that the immobilization efficiency of Cd using S-nZVIFe3++S2- (S/Fe = 0.14) reached the peak value of 99.54%. 1% and 5% dosages of S-nZVI significantly reduced Cd concentration in the overlying water, DTPA-extractable Cd content, and exchangeable (EX) Cd speciation (P < 0.05). Cd leaching in sediment and total iron in the overlying water remained at low levels during 90 d of incubation. Notably, each treatment maintained a high Cd immobilization efficiency under different pH, water/sediment ratio, organic acid, and coexisting ion conditions. Sediment physicochemical properties, functional bacteria, and a range of adsorption, complexation and precipitation of CdS effects dominated Cd immobilization.

Fabrication of abundantly functionalized dendritic biochar composites as adsorbents for the high-efficiency removal of heavy metal ions and dyes

A novel polymer modified biochar composite material (MNBC@p(HGMA-co-PSS-b-AA)) with dendritic structure, abundant functional groups and easy recovery was synthesized, which exhibited excellent removal capacity for Cr(VI), Lemon-Yellow (LY) and Malachite Green (MG). The prepared MNBC@p(HGMA-co-PSS-b-AA) was characterized via thermogravimetric analysis (TGA), scanning electron microscope (SEM) and Fourier transmission infrared spectra (FT-IR), proving to be with abundant functional groups and pore structure. The adsorption capacities for Cr(VI), LY and MG were 421.79, 1169.14 and 1231.53 mg/g, respectively, surpassing the capacities of most previously reported materials in recent years. Additionally, the effects of many factors on adsorption performance were explored. Experimental results indicated that the adsorption of Cr(VI), LY and MG on MNBC@p(HGMA-co-PSS-b-AA) followed pseudo-second-order and Langmuir models. Furthermore, MNBC@p(HGMA-co-PSS-b-AA) still displayed excellent removal capacity for Cr(VI), LY and MG after five reuse cycles. Moreover, different real water samples such as lake water, tap water were used to measure removal efficiency of Cr(VI), LY and MG. The results indicated that removal rates of Cr(VI), LY, and MG were not less than 86.26 %, 98.25 %, and 97.98 %. Meanwhile, MNBC@p(HGMA-co-PSS-b-AA) could maintain removal rate of 85.35 % even after continuously filtering a large number of pollutants solution in adsorption column, revealing its promising applicability for efficient removal of dyes and heavy metal ions. Surprisingly, MNBC@p(HGMA-co-PSS-b-AA) not only quickly adsorbed Cr(VI), but also enabled the concentration of Cr(VI) after adsorption to meet the World Health Organization standard for drinking water. Additionally, FT-IR and X-ray photoelectron spectroscopy (XPS) analysis suggested that adsorption mechanisms for Cr(VI) were hole filling, redox reaction and electrostatic interaction and adsorption mechanisms for LY and MG were hole filling, π–π interaction, π–π electron donor–acceptor (π–π EDA) interaction, electrostatic interaction and hydrogen bond.

Radiation synthesis of IDAA functionalized loofah sponge for enhanced removal of Pb(II) and Cd(II): Behavior and mechanism investigation

Biomass has been deemed as the most promising adsorbent for metal ions capture due to its environment-friendly and easy functionalization. Within this work, we combined a green and powerful radiation grafting-ring opening method that yields high-density functional groups containing a large number of carboxylic acid groups with loofah sponge (LFs) to achieve a novel functionalized loofah sponge (LFs-PGMA-IDAA) as a Pb(II)/Cd(II) adsorbent. The as-prepared biosorbent could efficiently capture Pb(II) and Cd(II) ions in wastewater. Moreover, the biosorbent could quickly reach adsorption equilibrium within 80 min, and the kinetics data fit well with the pseudo-second-order model. The thermodynamic parameters reveal that the adsorbing process is both spontaneous and endothermic. Moreover, the biosorbent possessed excellent removal capacities towards Pb(II)/Cd(II), and the maximum uptake capacity of Pb(II) and Cd(II) were 237.85 and 169.81 mg/g at 318.15 K, pH = 5, respectively. Furthermore, the excellent Pb(II)/Cd(II) binding of LFs-PGMA-IDAA was primarily due to complexation, ion exchange, electrostatic interaction and pore adsorption. This research presents that iminodiacetic acid modified LFs could be utilized as a high-performance biosorbent for capturing heavy metal ions. It might serve as an eco-friendly adsorbent in practical wastewater treatment fields.

Comprehensive review on lignocellulosic biomass derived biochar production, characterization, utilization and applications

Biochar is an ample source of organic carbon prepared by the thermal breakdown of biomass. Lignocellulosic biomass is a promising precursor for biochar production, and has several applications in various industries. In addition, biochar can be applied for environmental revitalization by reducing the negative impacts through intrinsic mechanisms. In addition to its environmentally friendly nature, biochar has several recyclable and inexpensive benefits. Nourishing and detoxification of the environment can be undertaken using biochar by different investigators on account of its excellent contaminant removal capacity. Studies have shown that biochar can be improved by activation to remove toxic pollutants. In general, biochar is produced by closed-loop systems; however, decentralized methods have been proven to be more efficient for increasing resource efficiency in view of circular bio-economy and lignocellulosic waste management. In the last decade, several studies have been conducted to reveal the unexplored potential and to understand the knowledge gaps in different biochar-based applications. However, there is still a crucial need for research to acquire sufficient data regarding biochar modification and management, the utilization of lignocellulosic biomass, and achieving a sustainable paradigm. The present review has been articulated to provide a summary of information on different aspects of biochar, such as production, characterization, modification for improvisation, issues, and remediation have been addressed.

Facile synthesis and life cycle assessment of Iron oxide-Douglas fir biochar hybrid for anionic dye removal from water

Development of low-cost and safe IONPs-based biochar hybrids with efficient multiple pollutant removal abilities is critical. In the present study, we studied the potential of an Fe3O4-modified wood-based biochar (FDBC) composite to remove an aqueous anionic dye, bromophenol blue (BPB) via simple magnets. Smaller surface area (1.5 times) and a smaller pore volume (∼2 times) of FDBC over the original biochar (DBC) does not impede the BPB uptake by FDBC. The Langmuir monolayer BPB adsorption capacities of FDBC and DBC are 448.0 and 451.0 mg/g (removal percentages, 89.8 % vs. 90.3 %) (adsorbent dose 50 mg, 25 mL of 1000 mg/L BPB concentration, 2 h, pH 5.0). The larger surface area (248 m2/g) and abundant nano Fe3O4 (11.0 nm) sites account for FDBC's excellent BPB removal compared to recent IONPs-based adsorbents. At pH 5.0–8.0, the BPB is bound to the FDBC (points of zero charge = 8.2) via H-bonding and π-π stacking, as confirmed by pH, desorption, and thermodynamic studies. Compared to NaOH and H2O2, methanol desorbs more BPB from the spent adsorbent at pH 7.0. Moreover, this composite removes even the BPB residuals from real wastewater, becoming an ideal adsorbent for BPB removal. A limited life cycle assessment of FDBC's synthesis revealed a higher impact for global warming (2.38 kg CO2eq) per kg of the adsorbent, whereas the lower impacts for ozone depletion, particulate matter emissions, and air quality. The FDBC is more economical because of its green and facile synthesis, excellent dye removal capacity, easy and fast recovery. Efficient multiple dye uptake of FDBC produces large concentration of recovered dyes, which can be possibly reused in various economic applications.

A comprehensive study on in situ synthesis of a magnetic nanocomposite of magnetite and reduced graphene oxide and its effectiveness at removing arsenic from water

In this study, the in situ synthesis of Fe3O4 nanoparticles on the surface of two-dimensional rGO nanosheets was performed. Fe3O4/rGO nanocomposites with a different degree of rGO reduction were obtained using various mass ratios between Fe3O4 and rGO, and different synthesis times. A comprehensive analysis of the morphology, microstructure, magnetic properties and the reduction degree of the synthesized rGO and Fe3O4/rGO nanocomposites was performed. The synthesis conditions were established for the preparation of a Fe3O4/rGO nanocomposite with the highest degree of rGO reduction and Fe3O4 phase purity. An increase in crystallite size and average particle size with the increase in the Fe3O4:rGO mass ratio (from 1:1 to 6:1) was revealed. For the first time, a saturation point for the amount of phase-pure Fe3O4 nanoparticles on the rGO surface was determined, as was a specific ratio of magnetite to rGO at which saturation occurred. Examination of the adsorption isotherms and kinetics indicated that the magnetic Fe3O4/rGO nanocomposite can serve as an effective adsorbent for arsenic ion (As3+) removal from water, with an excellent removal capacity of 14 mg g−1. In addition, the adsorption rate of the Fe3O4/rGO nanocomposite enabled 81% As3+ uptake within 1 min, which is superior to the literature data.

Interfacial Assembly of Nanocrystals on Nanofibers with Strong Interaction for Electrocatalytic Nitrate Reduction.

One-dimensional fiber architecture serves as an excellent catalyst support. The orderly arrangement of active materials on such a fiber substrate can enhance catalytic performance by exposing more active sites and facilitating mass diffusion; however, this remains a challenge. We developed an interfacial assembly strategy for the orderly distribution of metal nanocrystals on different fiber substrates to optimize their electrocatalytic performance. Using electrochemical nitrate reduction reaction (NO3 - RR) as a representative reaction, the iron-based nanofibers (Fe/NFs) assembly structure achieved an excellent nitrate removal capacity of 2317 mg N/g Fe and N2 selectivity up to 97.2 %. This strategy could promote the rational design and synthesis of fiber-based electrocatalysts.

Interfacial Assembly of Nanocrystals on Nanofibers with Strong Interaction for Electrocatalytic Nitrate Reduction

AbstractOne‐dimensional fiber architecture serves as an excellent catalyst support. The orderly arrangement of active materials on such a fiber substrate can enhance catalytic performance by exposing more active sites and facilitating mass diffusion; however, this remains a challenge. We developed an interfacial assembly strategy for the orderly distribution of metal nanocrystals on different fiber substrates to optimize their electrocatalytic performance. Using electrochemical nitrate reduction reaction (NO3−RR) as a representative reaction, the iron‐based nanofibers (Fe/NFs) assembly structure achieved an excellent nitrate removal capacity of 2317 mg N/g Fe and N2 selectivity up to 97.2 %. This strategy could promote the rational design and synthesis of fiber‐based electrocatalysts.

Treatment of real textile wastewater by coagulation/flocculation integrated with direct contact membrane distillation

ABSTRACT This study investigated the water recovery of real textile wastewater by Coagulation/Flocculation (CF) integrated with Direct Contact Membrane Distillation (DCMD). The proof-of-concept tests were studied with synthetic solutions of reactive and disperse black dyes at different concentrations, and real textile wastewater from the discharge machine and the equalization tank. Results showed that CF-DCMD exhibited higher permeate fluxes (up to 40%) than single DCMD and maximum color rejection rates (100%). Moreover, CF-DCMD enabled water reclamation from cotton and polyester dyeing wastewater which was not possible by MD (Membrane Distillation). The integrated system showed excellent chemical oxygen demand removal capacity, total suspended solids, turbidity, conductivity reduction, and removed any signs of toxicity from the tested wastewater. The coagulation/flocculation process prior to the MD reduced the fouling factor for all wastewater, highlighting the equalization tank where a reduction of around 72% was observed, achieving the goal of reducing fouling and increasing the efficiency of the MD. Membrane characterization indicated that CF-DCMD confirmed less fouling of membranes than single DCMD. Thus, this study allows to understand the potential and robustness of the CF-DCMD process in the treatment of textile wastewater and that it is possible to develop alternative technologies to treat complex wastewater effectively.

Superior Removal of Toxic Cr(VI) from Wastewaters by Natural Pine Bark

Hexavalent chromium (Cr(VI)) is one of the most toxic heavy metals found in industrial wastewater, so many researchers are working to develop efficient and environmentally friendly removal methods. It has been reported that natural biomass and its derivatives can be used to treat wastewaters containing Cr(VI). However, biomass with sufficient Cr(VI) removal performance to replace the existing chemical method, which is cheap and simple, has not been reported yet. This study reports that inexpensive, abundant, and commercially available pine bark has the highest Cr(VI) removal capacity (i.e., 376.3 mg/g) compared to biomass reported elsewhere. This value is six times higher than the theoretical value of an inorganic reducing agent (iron(II) sulfate heptahydrate). The main mechanism of Cr(VI) removal by pine bark was clearly identified through kinetic experiments, Fourier-transform infrared spectrometer, and X-ray photoelectron spectroscopy analyses, which were used to study the compositions, functional groups, and bonding states of pine bark. It was found that pine bark consists of various acidic functional groups that can act as electron donors to promote the removal of Cr(VI) through redox reactions. In conclusion, pine bark may be a promising candidate for the removal of Cr(VI) from wastewater, owing to its excellent removal capacity.

Engineering sulfuric acid-pretreated biochar supporting MnO2 for efficient toxic organic pollutants removal from aqueous solution in a wide pH range

Manganese dioxides (MnO2) and biochar materials are both desirable candidates for environmental remediation of toxic organic pollutants (TOPs) in water due to wide availability and environmental-friendly. In practical application, however, MnO2 suffers from low redox activity owing to deprotonation, while biochar is subject to limited removal capacity. Herein, a difunctional engineering sulfuric acid-pretreated biochar supporting MnO2 composite (MBC-A) was firstly synthesized and optimized to remove various TOPs from aqueous solution. Specifically, sulfuric acid not only served as an active agent to improve the specific surface area of biochar for improvement of adsorption capacity and more MnO2 loading, but also facilitated the introduction of sulfonic acid groups (-SO3H) as an internal proton reservoir to inhibit inactivation of MnO2 due to deprotonation in alkaline. Thanks to adsorption and oxidation, MBC-A showed excellent removal capacity (214.9 mg/g) and fast reaction kinetics (360 min) for tetracycline (TC), exceeding precursor and other materials reported in literature. Importantly, the effective operation pH range of MBC-A was broadened to 1–13 with the help of buffering capacity of –SO3H groups. The dominant driving force of adsorption were π-π interaction and hydrogen bond; while reactive oxidative species were mainly ascribed to singlet oxygen (1O2), hydroxyl radical (·OH) and reactive Mn3+. The possible reactive sites and pathway were investigated by combining experimental results with density functional theory (DFT) calculation. Further, the results of multiple cyclic runs, removal in real river water and toxicity assessment demonstrated well reusability, high environmental security, and excellent practical applicability of MBC-A.

An automated algorithm for the determination of oil absorption strategy of magnetic nanoparticles from SEM images

In recent years, the magnetic iron oxide nanoparticles (MNPs) are employed as efficient absorbents for oil removal from water. In this research, the particle size (diameter) obtained from Scanning Electron Microscopy (SEM) images of MNPs, before and after oil-absorption, are utilized to determine the oil-absorption capacity. However, the manual evaluation of the particle size and particle size distribution (PSD) are highly time-consuming and needs expertised people for accurate analysis. Hence, an image processing algorithm is employed for the determination of particle size and PSD from the Scanning Electron Microscopy (SEM) images. The key objective revolves with the preparation of the Maleic Anhydride Grafted Polypropylene anchored Magnetic Nanoparticles (MAPP-a-MNPs) to absorb crude oil from the marine water. The shape, size, and size distribution of MAPP-a-MNPs were assessed by both manual and automated analysis. For this purpose, expertise people help with the manual analysis and Threshold Adaptive-Canny Edge Detection (TA-CED) and Accumulator Updated-Circular Hough Transform (AU-CHT) method is employed for automated analysis. All the automated process were conducted in MATLAB and the measurements were taken for both before and after the oil absorption images. These measurements aid us to determine the quantity of oil absorbed by MAPP-a-MNPs. The results demonstrates excellent oil removal capacity of MAPP-a-MNPs.