Removal Of Organic Compounds Research Articles

Advanced Oxidation Processes and Adsorption Technologies for the Removal of Organic Azo Compounds: UV, H2O2, and GAC

This research focuses on the removal of emerging contaminants (CEC) present in synthetic aqueous matrices. Azole compounds were selected as CEC of interest due to their persistence and toxicity, particularly the triazole and oxazole groups. These compounds are also trace contaminants listed in the proposed revision of Directive 91/271/EEC on urban wastewater treatment and the 3rd European Union Observation List (Implementing Decision EU 2020/116), highlighting their regulatory importance. The draft Directive includes the implementation of quaternary treatments to achieve the highest possible removal rates of micropollutants. Among the technologies used on a large scale are some advanced oxidation processes (AOP), often combined with adsorption on activated carbon (AC). Laboratory-scale pilot plants have been designed and operated in this research, including UV photolysis and oxidation with H2O2 and adsorption with GAC. The results demonstrate that UV photolysis is able to remove all the selected CECs except fluconazole, reaching eliminations higher than 86% at high doses of 31.000 J/m2. Treatment by H2O2 achieved removals of 4 to 55%, proving to be ineffective in the degradation of persistent compounds when acting as a single technology. Adsorption by AC is improved with longer contact times, reaching removals above 80% for benzotriazole and methyl benzotriazole at short contact times, followed by sulfamethoxazole and tebuconazole. Fluconazole had a mean adsorption capacity at low contact times, while metconazole and penconazole showed low adsorption capacities.

Removal of heavy metals and organic compounds from wastewater printing circuit board manufacturers via a hybrid ferrate(VI)-trithiocarbonate process: An optimization study and toxicity assessment

Removal of heavy metals and organic compounds from wastewater printing circuit board manufacturers via a hybrid ferrate(VI)-trithiocarbonate process: An optimization study and toxicity assessment

Sintering Evolving Mn2O3-LaMnO3 Perovskite Heterointerfaces as Highly Active and Durable Catalysts for Catalytic Removal of Volatile Organic Compounds.

Improving the catalyst performance for the thermal oxidation reaction faces the daunting challenge of the activity-stability trade-off. Herein, an evolved heterointerface was constructed on spherical Mn2O3 nanocatalysts to achieve exceptional stability while maintaining adequate activity by simply introducing La. The generation of the active Mn3O4-Mn2O3 heterointerfaces by La doping was experimentally observed, which further segregates to the surface during thermal aging and forms epitaxially grown heterostructured LaMnO3-Mn2O3 with Mn atoms. The former can act as highly active sites for the deep oxidation of VOCs due to the richness in oxygen vacancies and Mn4+ ions, while the latter acts as the diffusion barrier to inhibit grain growth and produce advantageous reactive electronic structures around the interface. The La-modified Mn2O3 oxide reached 90% conversion in toluene oxidation at 286 °C under the high WHSV of 240,000 mL g-1 h-1 and slightly increased to 327 °C after thermal aging at 800 °C. This work provides a versatile strategy for fabricating effective oxidation catalysts with high low-temperature activity and antisintering properties for industrial applications.

Production of High Specific Surface Area Activated Carbon from Tangerine Peels and Utilization of Its By-Products

Biomass waste, generated globally in vast quantities, represents an underutilized yet highly valuable resource for advanced material production. This study highlights a novel valorization pathway for waste tangerine peels, sourced from Jeju Island, South Korea, by converting them into high-performance activated carbon (T-AC) with exceptional pore characteristics, specifically designed for volatile organic compound (VOC) removal. Utilizing a unique combination of hydrothermal carbonization (HTC) and dry carbonization (DC) processes, the structural properties of the biomass were optimized, significantly enhancing the fixed carbon content. Subsequent chemical activation with an alkaline agent yielded T-AC with an outstanding specific surface area (1530–3375 m2/g) and total pore volume (0.73–2.00 cm3/g), with a tailored pore distribution favoring the sub-mesopore range (2.0–4.0 nm). The T-AC demonstrated remarkable performance in removing methylene chloride (MC), a hazardous VOC, with methylene chloride activity (MA) increasing from 44.7% to 76.3% as the activation agent ratio increased, while methylene chloride working capacity (MWC) improved significantly from 17.1% to 55.9%. These results underscore the transformative potential of tangerine peel-derived AC as a sustainable solution for VOC remediation, combining environmental waste management with advanced adsorption technology. The findings not only advance the field of biomass utilization but also offer a scalable approach for tackling pressing environmental and industrial challenges.

Efficient and highly selective deep removal of hydrophobic organic compounds from leachate by polyamide microplastics

Efficient and highly selective deep removal of hydrophobic organic compounds from leachate by polyamide microplastics

Enhancing reactive oxygen release-replenishment and Lewis acid acidity by Nb doping in NbmCeOx for simultaneous elimination of NOx and toluene

Multi-pollutant control (MPC) is a promising technology for the simultaneous removal of nitrogen oxidation (NOx) and volatile organic compounds (VOCs) in fossil and biomass fuel combustion. This study uses Nb doping CeO2 bimetallic oxide catalysts to meet low-temperature NH3-SCR de-NOx, catalytic toluene oxidation and simultaneous elimination of NOx and toluene. X-ray diffraction (XRD), Raman and transmission electron microscopy (TEM) are applied to confirm the Nb doping into the lattice of CeO2 for Nb0.034CeOx and Nb0.36CeOx, but excess Nb in polymeric state NbOx present in Nb0.36CeOx. The effects of Nb doping on surface adsorbed oxygen, surface lattice oxygen and bulk phase lattice oxygen were investigated by XPS, EPR, O2-TPD, H2-TPR and DFT calculations. Using in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), it is investigated that the surface reactive oxygen species (including surface adsorbed oxygen and surface lattice oxygen) participates in NO oxidation, NH3 activation and toluene oxidation process. The reaction mechanism of NH3-SCR de-NOx, toluene oxidation and multi-pollutant co-elimination processes, as well as interactions between multiple reactants in the MPC reaction, were also studied with in-situ DRIFTS. It is found that Nb doping contributes to the mobility of lattice oxygen, which favors the oxidation of NH3 to NH2 and the release and rapid replenishment of reactive oxygen species at temperature ≥ 210 °C. The strong Lewis acid sites (Nb5+) promote the adsorption of NH3 species and their stability. These facilitate the NH3-SCR de-NOx in a wide temperature range and achieve the elimination of multiple pollutants on Nb0.034CeOx. So, Nb0.034CeOx exhibits matching activity temperature window in 170–390 °C for MPC (100 ppm toluene and 1000 ppm NO) over 90 % NO and toluene conversion in wet condition. Polymeric NbOx inhibits the activity of surface adsorbed oxygen and surface lattice oxygen and weakens the acidity of Lewis acid, therefore leading Nb0.36CeOx to poor performance of toluene oxidation and NH3-SCR at low-temperature.

Multifunctional superhydrophobic sugarcane bagasse capable of efficiently separating oil-water mixtures and degrading MB

Biodegradable and low-cost superhydrophobic absorption materials are still urgently required for the removal of organic compounds from sewage. In this study, sugarcane bagasse (SCB), an abundant and readily available byproduct from sugarcane industries, was used as substrate to fabricate the superhydrophobic adsorbent through a facile dip-coating technique. Firstly, β-FeOOH particles were in-situ grown on the SCB surface, which was further decorated with SiO2 particles. Next, the modified SCB were coated with benzoxazine based on cardanol and dodecylamine (CD) followed by a thermal curing to obtain a superhydrophobic SCB (PC-D/β-FeOOH@SiO2/SCB) with a water contact angle (WCA) of 154°. PC-D/β-FeOOH@SiO2/SCB not only exhibited excellent oil absorption capacities in the range of 11.8 to 22.6 g/g for various organic solvents and oils, but also could successfully separate immiscible oil-water mixtures and emulsions with a separation efficiency of over 99.1 %. After 30 cycles of use, the absorption capacity of the modified SCB only displayed a slight decrease and its separation efficiencies for immiscible oil-water mixture, water-in-oil and oil-in-water emulsions are all more than 99.2 %, meanwhile, all these repeatedly used SCB still maintained a superhydrophobicity, demonstrating an outstanding reusability. Moreover, the WCA of PC-D/β-FeOOH@SiO2/SCB was still higher than 150o after 48 h of immersion in HCl, NaOH and NaCl solutions, exhibiting a satisfactory chemical stability. Besides, the prepared SCB also possessed a high photocatalytic degradation activity to methylene blue. Therefore, this work not only provides a sustainable and cheap superhydrophobic absorbent for wastewater treatment, but also presents a route for the better utilization of SCB.

Removal of fluoride, cadmium and triclosan from water using bone chars from an invasive species: Optimization, equilibrium and adsorption mechanisms

The bone char used in this study was synthesized from devilfish, an invasive species, as an alternative source of raw material for use as an adsorbent for fluoride, cadmium and triclosan from water. Response surface methodology (RSM) was employed to optimize the synthesis conditions such as temperature and pyrolysis time in a tube furnace, ranging from 600 to 800 °C and 1–3 h, respectively. The maximum experimental adsorption capacities of fluoride, cadmium and triclosan (qF, qCd and qTCS) were 7.41, 124.59 and 6.26 mg g−1 obtained at temperatures and times of 600 °C and 1 h, 600 °C and 3 h and 700 °C and 1 h, respectively. The maximum %Y was 70.26 % obtained at 600 and 3 h. Analysis of variance revealed the significance of the synthesis temperature on the adsorption capacities and yield, while the oven residence time was not significant. It was predicted from a multi-objective statistical model that the optimal temperature and time conditions of 627 °C and 3 h maximize the values of %Y, qF, qCd and qTCS corresponding to 68.7 %, 6.47, 117 and 4.35 mg g−1, respectively. The physicochemical and textural properties of the bone char indicated a basic and mesoporous surface. TGA, FT-IR, SEM, and EDS analyses confirmed the adsorption of fluoride and cadmium by electrostatic attractions, ion exchange, and chemisorption, while triclosan was attributed to Van der Waals forces, H-bond and π-π interactions due to the nature of its structure. These results highlight the versatility of devilfish bone char for the removal of anions, cations, and organic compounds, suggesting its potential as a management alternative for this invasive species.

In situ dual-utilize of ZnCl2 for preparation of ZIF-8 functionalized biomass-based porous carbon for adsorption removal of volatile organic compounds

In this study, ZnCl2 was successfully dual-used for the chemical activation of biomass-based activated carbon (BAC) and ZIF-8 synthesis to prepare the functionalized porous carbon composite PC-Z/W. The findings indicated that the chemical activator ZnCl2 be directly recycled for the synthesis of ZIF-8 on BAC. The ZIF-8 functionalization provided the PC-Z/W composites with a well-developed porous structure and rich N- and O-containing surface functional groups, which enabled the PC-Z/W to exhibit superior adsorption properties (large adsorption capacity, temp adaptability, and competitive adsorption with water) for low-concentration gaseous pollutants. The PC-Z/W(P1000) exhibited the best adsorption performance for toluene, with a saturation adsorption capacity (qs) of 277 mg/g at 25 °C and retained 70 % of qs (192 mg/g) at 80 °C. It also has exceptional adsorption capabilities for acetone (qs = 170 mg/g) and ethyl acetate (qs = 227 mg/g), enabling it to show superior multi-component adsorption behavior and effective competition with water. In addition to VOCs, PC-Z/W is also noteworthy for the adsorption of inorganic substances like SO2 (203 mg/g) and CO2 (4.65 mmol/g), greatly broadening its application prospects.

Current regulates electron donors for heterotrophic and autotrophic microorganisms to enhance sulfate reduction in three-dimensional electrode biofilm reactors

The variability in industrial production often generates wastewater with an unstable carbon-to-sulfur ratio, challenging the concurrent removal of sulfate and organic compounds. Three-dimensional biofilm electrode reactor (3D-BER) technology offers a promising solution, compatible with both autotrophic and heterotrophic sulfate reduction. In this study, four up-flow 3D-BERs with gradient current levels were operated for nearly 400 days to treat simulated high-concentration sulfate wastewater. The effects of current intensity, hydraulic retention time (HRT), and influent carbon-to-sulfur ratio on sulfate and organic removal were investigated. The composition and functions of microbial communities were analyzed by metagenomic sequencing. The synergistic mechanism between heterotrophic and autotrophic sulfate reduction was examined by delineating their individual contributions to sulfate removal. Under optimized conditions (HRT 60 h, influent carbon-to-sulfur ratio of 1.7, and current intensity of 50 mA), the highest removal efficiencies for SO42- and COD reached 70.47 % and 85.58 %, respectively. Elevated current intensity increased the abundances of Desulfuromonadaceae, Desulfovibrionaceae and Methanobacteriaceae, while decreasing Anaerolineaceae and Geobacteraceae. Key genes involved in carbon fixation and hydrogen-relied sulfate reduction showed lower abundances at high current levels, whereas genes for direct electron uptake from the electrode were more abundant. Batch experiments demonstrated a synergistic effect between autotrophic and heterotrophic sulfate reduction, most pronounced at 50 mA. Our work successfully regulates electron donors for microbial reduction of high-concentration sulfate in 3D-BERs by manipulating current intensity, providing new insights into the application of bioelectrochemical technology for complex industrial wastewater treatment.

High removal of volatile organic compounds on hierarchical carbons prepared from agro-industrial waste of banana fruit production for air decontamination.

Activated carbons were prepared from residues from agro-industrial banana production (banana pseudostem) and evaluated in the capture of five different volatile organic compounds (VOCs): dichloromethane, chloroform, ethyl acetate, hexane, and cyclohexane. The biomass was first submitted to a hydrothermal treatment in the presence of KOH or ZnCl2 as activating agents, followed by a dry pyrolysis. This new advance in methodology contributes to producing activated carbons with hierarchical porosity and high surface areas (701-1312 m2g-1), promoting increased interest in managing waste from banana fruit agricultural production. VOC capture studies were performed by thermal analysis, and capture capacities were similar to or higher than those presented in the literature. Higher adsorption capacities were related to the amount of available micropores, and the capture capacity was enhanced by the contribution of small mesopores. As the highest adsorbed amounts of dichloromethane (933mgg-1 at 25°C) were obtained for the material activated with ZnCl2 (1:3), further studies were carried out for this system. The experimental data was fitted using a pseudo-first-order kinetic model. A study was carried out in different atmospheres (He, N2, air), showing that co-adsorption is occurring. Under simulated environmental conditions, the capture capacity decreased slightly at equilibrium, and the new adsorbent was used for up to ten cycles without significantly losing its efficiency, indicating good application in the field.

Hydrodynamics and mass transport in an anodic oxidation reactor: Influence of gas evolution and flow path through mesh electrodes

Removal of organic compounds by anodic oxidation requires a sufficiently high rate of mass transport of target compounds to the electrode surface. Since anodic oxidation is often accelerated by the formation of hydroxyl radicals from water oxidation at high anodic potential, the role of oxygen/hydrogen evolution reactions was investigated. Residence time distributions showed that formation of bubbles in zones where fluid velocity was minimal, allowed for strongly improving global hydrodynamics in the reactor. The role of bubbles was also discussed by comparing mass transport coefficients obtained from the limiting current technique to values obtained from kinetics of COD removal during treatment of a model pollutant (phenol). The use of mesh electrodes (with liquid flowing through the electrode) further promoted convection and mass transport of organic compounds compared to plates. However, large bubbles generated at the surface of the plate electrodes also enhanced convection in their vicinity. In both cases, an adverse effect from bubble adhesion was observed because of the decrease in the active surface of electrodes. The mass transport coefficient obtained with the limiting current technique using mesh electrodes was 0.69 × 10−3 cm s-1 at 10.8 L h-1 with a mean velocity of electrolyte past the mesh surface (u¯mesh) of 0.37 cm s-1. It decreased to 0.58 × 10−3 cm s-1 during the treatment of phenol at the same flow rate and reached 0.75 × 10−3 cm s-1 when increasing the flow rate to 32.4 L h-1. By taking into consideration gas evolution at the surface of electrodes, this study allowed for accurate calibration of an advective – dispersive model with reaction that could be used for sizing such reactors according to the intended application.Abbreviations: Ae, the volumetric surface area (ratio between the geometric volume and the active surface area of the mesh electrodes) (cm−1); CA, aeration by a floor diffuser of fine bubbles and no current at the electrodes; CEP, polarization of the electrodes with a current intensity and no aeration; CW, no electrode polarization and no aeration; COD, chemical oxygen demand (mgO2 L−1); Di, diffusion coefficient of specie i (m2 s-1); D, dispersion coefficient (cm2 min−1); E(θ), residence time distribution function; EC, electrical energy consumption (kWh gCOD−1); F, Faraday constant (96485 C mol−1); HER, hydrogen evolution reaction; IOA, index of agreement; km, mass transport coefficient (m s-1); MCE, mineralization current efficiency; ME, model efficiency; OER, oxygen evolution reaction; OH, hydroxyl radical; Ql, liquid flow rate (L h-1); rAO: anodic oxidation rate (mol m−3 s−1); RTD: residence time distribution; ts¯: mean residence time or first moment order; u¯: mean flow velocity (m s-1); VT: total volume (L); σ2: variance or second moment order; γ: skewness factor or third moment order; τ: residence time; μ: order moment.

Microdroplet-Mediated Multiphase Cycling in a Cloud of Water Drives Chemoselective Electrolysis.

Electrification of water in clouds leads to fascinating redox reactions on Earth. However, little is known about cloud electrochemistry, except for lightning, a natural hazard that is nearly impossible to harness. We report a controllable electrochemistry that can be enabled in microclouds by fast phase switching of water between the microdroplet, vapor, and bulk phase. Due to the size-dependent charge transfer between droplets during atomization, this process generates an alternating voltage arising from the self-electrification and discharging of microdroplets, vapor, and bulk phase by electron and ion transfer. We show that the microclouds with alternating voltage cause 1,2-dichloroethane (ClH2C-CH2Cl) to be converted to vinyl chloride (H2C═CHCl) at ∼80% selectivity. These findings highlight the importance of controlled cloud electrochemistry in accelerating the removal of volatile organic compounds and treating contaminated water. We suggest that this work opens an avenue for harnessing cloud electrochemistry to solve challenging chemoselectivity problems in aqueous reactions of environmental and industrial importance.

Exploring the Possibilities of Using Recovered Collagen for Contaminants Removal—A Sustainable Approach for Wastewater Treatment

Collagen is a non-toxic polymer that is generated as a residual product by several industries (e.g., leather manufacturing, meat and fish processing). It has been reported to be resistant to bacteria and have excellent retention capacity. However, the recovered collagen does not meet the requirements to be used for pharmaceutical and medical purposes. Due to the scarcity of water resources now affecting all continents, water pollution is a major concern. Another major field that could integrate the collagen generated as a by-product is wastewater treatment. Applications of collagen-based materials in wastewater treatment have been discussed in detail, and comparisons with already frequently used materials have been made. Over the last years, collagen-based materials have been tested for removal of both organic (e.g., pharmaceutical substances, dyes) and inorganic compounds (e.g., heavy metals, noble metals, uranium). They have also been tested for the manufacture of oil-water separation materials; therefore, they could be used for the separation of emulsified oily wastewater. Because they have been analysed for a wide range of substances, collagen-based materials could be good candidates for removing contaminants from wastewater streams that have seasonal variations in composition and concentration. The use of recovered collagen in wastewater treatment makes the method eco-friendly and cost efficient. This paper also discusses some of the challenges related to wastewater treatment: material stability, reuse and disposal. The results showed that collagen-based materials are renewable and reusable without significant loss of initial properties. In the sorption processes, the incorporation of experiments with real wastewater has demonstrated that there is a significant competition among the substances present in the sample.

The Influence of Thermal Treatment of Activated Carbon on Its Electrochemical, Corrosion, and Adsorption Characteristics

Activated carbons can be applied in various areas of our daily life depending on their properties. This study was conducted to investigate the effect of thermal treatment of activated carbon on its properties, considering its future use. The characteristics of activated carbon heat-treated at temperatures of 1500, 1800, and 2100 °C based on its future use are presented. The significant effect of the treatment temperature on morphological, adsorption, electrochemical, and corrosion properties was proved. Increasing the temperature above 1800 °C resulted in a significant decrease in the specific surface area (from 969 to 8 m2·g−1) and material porosity—the formation of mesopores (20–100 nm diameter) was observed. Simultaneously, adsorption capability, double layer capacity, and electrochemically active surface area also decreased, which helped to explain the shape of cyclic voltammograms recorded in 2,4-dichlorophenoxyacetic acid and in supporting electrolytes. However, a significant increase in corrosion resistance was found for the carbon material treated at a temperature of 2100 °C (corrosion current decreased by 23 times). Comparison of morphological, adsorption, corrosion, and electrochemical characteristics of the tested activated carbon, its applicability as an electrode material in electrical energy storage devices, and materials for adsorptive removal of organic compounds from wastewater or as a sensor in electrochemical determination of organic compounds was discussed.

Titania stabilized Pickering emulsion for photocatalytic degradation of o-xylene

Efficient removal of insoluble volatile organic compounds (VOCs) from wastewater is a significant environmental challenge. In this work, we exploit the synergistic effect of photocatalysis and the high interfacial area of TiO2-stabilized Pickering emulsion to achieve efficient degradation of o-xylene, typically present in wastewater discharged from many industries. Interfacial photocatalysis is carried out by considering o-xylene in water Pickering emulsions stabilized by commercial titania nanoparticles in a multitube non-stirred reactor setup. Stable emulsions used for catalysis are formulated by optimizing o-xylene volume fraction, TiO2 concentration, pH, and homogenization conditions. The influence of photocatalyst loading, emulsion droplet size, and reaction conditions are systematically examined to determine their influence on the rate of photocatalytic degradation of o-xylene. Due to enhanced photocatalytic activity compared with conventional stirred batch photocatalysis, the TiO2-stabilized Pickering emulsion is found to increase the degradation rate and removal efficiency of o-xylene significantly. Furthermore, the Pickering emulsion stability during the photocatalytic process is studied, demonstrating the capacity of the emulsions to maintain stability and catalytic activity over a longer time period. The distinctive characteristics of Pickering emulsions – excellent storage stability and enhanced photocatalytic activity – make them a promising option for advanced wastewater treatment. The findings lead to the development of ecologically acceptable and sustainable VOC degrading strategies, which might be used in industrial and home wastewater treatment systems.

Catalytic performance of FeCo2O4 spinel cobaltite for degradation of ethylparaben in a peroxymonosulfate activation process: Response surface optimization, reaction kinetics and cost estimation

The presence of cosmetics and personal care products in water resources has become an increasing concern for environment due to their toxicity and persistence in aquatic medium. Peroxymonosulfate mediated advanced oxidation methods have a great potential for the efficient removal of complex organic compounds due to the generation of highly reactive radicals with high oxidation ability. Iron cobaltite, FeCo2O4 catalyst was used as a peroxymonosulfate (PMS) activator for the degradation of ethylparaben which was selected as a model personal care product ingredient. Paraben degradation was modelled and the optimum operating parameters were determined by using Box-Behnken design. The ethylparaben degradation efficiency was calculated as 94.6 % under the optimized conditions which were determined as 0.9 g/L FeCo2O4 loading, pH 6.15, and 0.26 g/L PMS dosage. The ethylparaben degradation reaction followed second-order reaction kinetics. The activation energy was evaluated as 40.1 kJ/mol. Quenching radical tests showed that the dominant reactive species were hydroxyl radicals. Toxicity of the treated samples in terms of L. sativum growth inhibition was evaluated as 1.5 %. The total cost of the treatment including the operating and the amortization costs was calculated as 0.91 €/L.

Effective removal of organic compounds by g-C3N4-AQ/Fe(III) via photocatalytic oxidation and photochemical cycling of iron

Anthraquinone-anchored graphitic carbon nitride (denoted as g-C3N4-AQ), which has been reported in the photochemical production of H2O2, demonstrated significant visible light photocatalytic activity with Fe(III) for the degradation of organic compounds. The synthesized g-C3N4-AQ exhibited a light absorption spectrum and crystallinity comparable to that of pristine g-C3N4. FT-IR and XPS analyses confirmed the covalent bonding between AQ and g-C3N4. The synthesized g-C3N4-AQ generated 12 μM of H2O2 within 2 h under visible light illumination, a quantity negligible for the degradation of organic compounds. However, in the combination with Fe(III), the system successfully degraded organic compounds, achieving degradation of 88 – 99 % in the presence of dissolved oxygen. It was also observed that the photochemical activity of g-C3N4-AQ/Fe(III) was non-selective towards the target organic compounds. Intriguingly, the visible light-illuminated g-C3N4-AQ/Fe(III) selectively degraded target organic compounds in the absence of dissolved oxygen. Experimental work employing reactive oxidant scavengers and oxidant probes revealed that •OH is the main reactive species responsible for the degradation of organic compounds in the presence of dissolved oxygen, whereas in its absence, the hole acts as the primary oxidant in the selective degradation of organic compounds. This finding provides important insights into the application of the g-C3N4-AQ/Fe(III) system for effective micropollutant removal.

Enhanced Removal of Refractory Organic Compounds from Coking Wastewater Using Polyaluminum Chloride with Coagulant Aids

This study explores the enhanced removal of refractory organic compounds from coking wastewater using polyaluminum chloride (PACl) with two different basicity levels (0.5 and 2.5), in combination with coagulant aids such as cationic polyacrylamide (CPAM) and iron ions. The results demonstrated that both PACl formulations significantly outperformed commercial PACl in terms of COD and color removal, with PACl at the basicity of 2.5 achieving slightly higher efficiency than PACl at the basicity of 0.5. The improved performance was attributed to the higher content of polymeric aluminum species, enhancing charge neutralization and bridging adsorption. The addition of coagulant aids further improved the performance, with PACl at the basicity of 2.5 combined with iron ions achieving the highest COD (48.41%) and color removal (80.77%), due to sweep coagulation and complexation. Organic composition analysis using gas chromatography–mass spectrometry (GC-MS), three-dimensional excitation–emission matrix (3D-EEM) fluorescence spectroscopy, and ultraviolet (UV) spectroscopy indicated that PACl combined with iron ions was the most effective in removing polycyclic aromatic hydrocarbons (PAHs) and nitrogen-, oxygen-, and sulfur-containing heterocyclic compounds. Additionally, a floc analysis showed that the flocs formed with iron ions were more compact and had better settleability compared to those formed with CPAM, further contributing to the improved coagulation efficiency. These results highlight the importance of optimizing the PACl basicity and coagulant aid selection for the enhanced removal of refractory organic compounds from coking wastewater, offering a promising strategy for advanced wastewater treatment.

A soft processing technology for the extraction of cellulose from plant residues and agri-food wastes

In this study, cellulose was extracted from giant cane (GC), Posidonia oceanica seagrass (PO), coffee silverskin (CS), and brewer's spent grain (BSG) as alternatives to conventional sources of cellulose. The extraction protocol involved three steps: i) hemicellulose and lignin removal through alkaline hydrolysis in a 5% (w/v) NaOH solution (solid-to-liquid ratio = 1:100 g/mL, T = 25 °C, t = 2 h, ω = 300 rpm), ii) removal of organic compounds and ashes through a 95% (v/v) ethanol solution (solid-to-liquid ratio = 1:25 g/mL, T = 25 °C, t = 0.5 h, ω = 500 rpm), and iii) double bleaching in a 1% (w/v) acidic (pH = 4) NaClO2 solution (solid-to-liquid ratio = 1:50 g/mL, T = 90 °C, t = 1.5 h, ω = 500 rpm). Yield, purity, crystallinity degree, and morphology of cellulose extracted through a soft-chemical cascade process were assessed by gravimetric, infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. Averaged cellulose extraction yields of 36.4, 38.6, 23.1, and 22.2% for GC, PO, CS, and BSG were obtained, respectively. All cellulose samples had high purity, though lower than the ultra-pure bacterial cellulose, which was due to the slight contamination from unremoved hemicellulose and lignin residues. Cellulose samples exhibited similar chemical features and the typical fibril-like morphology of microcrystalline cellulose (6–13 μm in width). The versatility of the proposed extraction procedure supports the sustainable conversion of low-cost organic biomasses to valuable products with manifold industrial applications (e.g., food packaging).