Initial Solution pH Research Articles

Comparison of naphthalene degradation by hydrogen peroxide, nano-calcium peroxide, peroxydisulfate, and peroxymonosulfate in the Fe(II)-citric acid catalytic environments

Abstract Naphthalene (NAP) was chosen as a target contaminant due to its increasing environmental concern in this work. Using hydrogen peroxide (H2O2), nano-calcium peroxide (nCP), peroxydisulfate (PDS), and peroxymonosulfate (PMS) as oxidants activated by Fe(II)-citric acid (CA) in aqueous solution, 92.8, 95.0, 97.5, and 99.9% of NAP were removed, respectively, in which CA could significantly enhance NAP degradation. HO• was demonstrated to be the major radical responsible for NAP removal in H2O2/Fe(II)/CA and nCP/Fe(II)/CA processes; both HO• and SO4•− were major radicals in PDS/Fe(II)/CA process, whereas SO4•− was the sole dominant radical in PMS/Fe(II)/CA process. The impacts of water matrices (anions, natural organic matters, and surfactants) and initial solution pH on NAP removal as well as the practicalities of these four systems in groundwater were explored. The efficient NAP degradation of nCP/Fe(II)/CA and PMS/Fe(II)/CA processes in the actual groundwater indicated that these two systems have great potential and advantages in the remediation of NAP-contaminated groundwater.

Modelling and optimization of Victoria blue uptake using response surface methodology (RSM) with novel magnetic folic acid-mannitol/mosquito coil ash nanocomposite

Recently, natural, and environmentally safe polymer-metal oxide hybrid nanocomposites have been increasingly noticed as cost-effective adsorbents for pollutant removal. In this context, a novel hybrid nanocomposite was prepared from a FAM copolymer synthesized by thermal poly-esterification and FAM-MCA/Fe3O4 obtained by the simple in-situ co-precipitation method. Following its structure elucidation using XRD, the nanomaterials were further characterized by FTIR and their surface analysis by using SEM-EDX, TEM and BET methods. The physicochemical characterization of the nanohybrid was accomplished and its performance and effectiveness in removing VB dye from simulated effluents was evaluated. The reaction surface method was used to optimize the operating conditions in terms of contact time (59.9 min), initial concentration VB (60 mg/L), dose of nanocomposite (0.15 g/L), and initial solution pH (6.0). The equilibrium results modelled with nonlinear isothermal and kinetic models complied well with the Langmuir isotherm and pseudo-second-order kinetics with both intraparticle and film diffusion driving the adsorption process. The enhanced adsorption performance of the NC was demonstrated by the significantly higher Langmuir saturation capacity (FAM-MCA/Fe3O4: 279; Fe3O4: 244 mg VB /g) at 303 K compared to other previously reported adsorbents and the strong recyclability while maintaining the adsorption effectiveness of 61.46 % up to five consecutive cycles. Using the deduced thermodynamic parameters, an exothermic, spontaneous, and practicable VB elimination process was established. The adsorption process was principally controlled by electrostatic contact, Yoshida H-bonds, dipole-dipole, n-π stacking, cation-π and, π-π interactions. A complete cost study was performed to assess the economic viability of the adsorbents. FAM-MCA/Fe3O4 was discovered to be the most affordable (551 INR/kg) approach for VB removal. The investigative findings unveiled that the as synthesized hybrid nanocomposite was a potent adsorbent for effective and efficient liquid-phase amputation of VB.

One-pot in situ synthesis of an NS-ligand co-doped metal-organic framework for the enhanced adsorption-assisted photocatalytic decontamination of metronidazole.

Doping active agents into metal-organic frameworks (MOFs) is widely sought after owing to its potential to enhance adsorption and photocatalytic efficiency, surpassing the potential of bare frameworks. This study incorporated a catalytically active NS-ligand (1,2-benzisothiazolin-3-one) into a very stable and porous PCN-600 MOF via an in situ synthesis approach. The NS-ligand, which matched with the host ligands of PCN-600, enabled the highly efficient synthesis of NS-co-doped MOFs. The pristine PCN-600 framework and morphology were retained in the MOF altered with the NS-ligand, as demonstrated by XRD, FTIR, and SEM characterizations. A high electron density was generated due to the synergistic effect between the defects in the NS-co-doped photocatalyst and engineered active sites. This facilitated the adsorption-assisted photocatalytic decontamination of metronidazole with an 87% removal by PCN-600-NS-10 compared to 43% by pristine PCN-600 within a total time of 150 min. The MOF doped with the NS-ligand exhibited a reduced band gap and enhanced adsorption and photocatalytic capabilities compared to pristine PCN-600. The impact of operational parameters, such as catalyst dosage, initial solution pH, and MNZ concentration, was also explored. Pseudo-second and pseudo-first order models were found to describe the adsorption and degradation kinetics of metronidazole and the Dubinin-Radushkevich model was found to fit the equilibrium adsorption results. The thermodynamic characteristics of adsorption processes (ΔGads, ΔHads, and ΔSads) demonstrated that adsorption was physical, spontaneous, and exothermic and resulted in increased entropy.

Hydrothermal preparation of Nb5+-doped α-Fe2O3 nanorods for efficient visible light-driven photocatalytic reduction of hexavalent chromium

Nb5+ doped α-Fe2O3 (Nb-Fe2O3) nanorods with different Nb5+ contents were prepared using a low-temperature, short-time, one-pot hydrothermal method. All the prepared Nb-Fe2O3 products showed better photocatalytic activities than α-Fe2O3 nanorods in the reduction of aqueous Cr(VI) under visible light (wavelength > 420 nm). 4% Nb-Fe2O3 had the maximum photocatalytic activity, which was 2.24 times that of α-Fe2O3 nanorods and surpassed those of many newly reported visible light photocatalysts. Moreover, the photocatalytic efficiency of 4% Nb-Fe2O3 can be further improved by proper increasing its dosage, decreasing the initial pH and Cr(VI) concentration of K2Cr2O7 solution. Furthermore, 4% Nb-Fe2O3 showed rather good photocatalytic stability and reusability. Besides, 4% Nb-Fe2O3 was efficient in visible light-driven photocatalytic reduction of Cr(VI) in diluted black chrome plating solution. Nb5+-doping can efficaciously enhance the abilities of α-Fe2O3 in absorbing visible light and transferring and separating photogenerated carriers, thereby contributing to the elevated photocatalytic activity of Nb-Fe2O3.

Valorization of Silybum marianum seed shells waste as biosorbent for basic fuchsin dye removal from water: kinetics, isotherms, and thermodynamic studies

Over the last decades, the valorization of agro-industrial wastes into adsorbents has received a lot of attention due to the low-cost, high performance and sustainability factors. This work aims to valorize Silybum marianum seed shells (SMSS) as biosorbent for the removal of basic fuchsin dye (BF) from water. The prepared biosorbent from SMSS was characterized to check the morphological and structural proprieties using several techniques including FTIR, XRD, SEM, TGA-DTA, and BET. It was found that SMSS has a fibrous semi-amorphous structure typical of lignocellulosic materials. The study also investigated the impact of numerous operational parameters on basic fuchsin biosorption efficiency, including particle size, biosorbent mass, stirring speed, initial dye concentration, temperature, and pH of solution. Additionally, the research explored the influence of natural water matrices on dye removal. The adsorption performance was found to be higher at basic pH values, reaching 97.50%. The adsorption process was analyzed using different kinetic models, and it was found that the process follows a pseudo-second-order model. The experimental data was thoroughly scrutinized using the Freundlich and Langmuir isotherm models. The results confirm that Langmuir model fits well the BF dye adsorption on SMSS surface. The thermodynamic study revealed that the adsorption process of BF dye onto SMSS was endothermic. Overall, SMSS shows great adsorption ability which might be a good candidate for real wastewater treatment, by considering low-cost and availability of the original waste.

A performance comparison of photo-fenton decolorization of methylene blue by using bentonite/iron composites prepared by liquid phase and solid phase ion exchange method

Nowadays, there is a wide range of pollutants present, which requires the treatment of wastewater. The photo-Fenton method has been recognized as valuable in this area. In this study, iron/bentonite composites were created using both liquid phase and solid phase iron exchange techniques, and they were utilized as a photocatalyst for the degradation of methylene blue through photo-Fenton process. Various factors affecting the photocatalytic decolorization were investigated, including the initial concentration of the dye, weight of the catalyst, pH of the solution, and concentration of hydrogen peroxide. The decolorization efficiency of the iron/bentonite composites prepared using the solid phase and liquid phase ion exchange approaches was found to be 99% and 95%, respectively. Based on the data, it can be concluded that the performance of both catalysts was almost equally influenced by the initial dye concentration, catalyst weight, solution pH, and hydrogen peroxide concentration. Moreover, the solid phase ion exchange method demonstrated greater reusability compared to the liquid phase ion exchange method. Consequently, it can be stated that the solid phase ion exchange approach is a suitable and straightforward alternative to the conventional liquid phase ion exchange method for producing a photo-Fenton catalyst.

Upcycling of sugar refining mud solid waste as a novel adsorbent for removing methylene blue and Congo red from wastewater.

The feasibility of utilizing the mud solid waste (MSW) produced during the carbonation process of sugar refining as a cost-effective and environmentally friendly alternative for the water removal of methylene blue (MB) and Congo red (CR), being highly utilized organic dyes representing cationic and anionic species, respectively is presented. Prior to its use, the MSW was dried at 110 °C for 24 h and sieved through a 100-mesh screen. The chief constituent of the MSW utilized was CaCO3, with a point of zero charge (PZC) found at pH 8.4 and 7.96 m2 g-1 total surface area. XRD and FTIR data indicate the presence of interactions between the dyes and the MSW surface, indicating effective adsorption. Different variables, such as initial dye concentration, MSW weight, solution pH, contact time, and temperature, were all examined to determine the optimal dye removal conditions. A central composite design (CCD) approach based on response surface methodology (RSM) modeling was utilized to identify statistically significant parameters for MB and CR adsorption capacities onto the MSW adsorbent. The removal equilibrium was typically reached in 120 minutes, with the greatest removal efficiency of CR taking place at pH 2 and 328 K, while the highest MB removal efficiency was obtained at pH 12 and 296 K. Kinetic studies suggest the adsorption of both dyes on the MSW follow pseudo-second-order rates, as evident through the high correlations obtained. Linearized and non-linearized Langmuir models showed strong correlations indicating maximum adsorption capacities of 86.6 and 72.3 mg g-1 for MB and CR, respectively. High regeneration and reusability potential of the MSW was demonstrated especially for the adsorption of CR, where the removal efficiency was nearly constant throughout five adsorption cycles, ranging from 93 to 91%, while the reduction in the removal for MB was much more significantly impacted, diminishing from 95 to 79% after the five cycles.

Preparation and application of KCC-1@ZIF-8 for the solid extraction of tetracycline with high adsorption capacity.

In this study, three different materials were prepared: dendritic fiber-type silica (KCC-1), zeolitic imidazolate framework-8 (ZIF-8), and a new composite material called KCC-1@ZIF-8. These materials were synthesized using microemulsion, stirring, and coating methods, respectively. The properties of the materials were characterized using various techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), TGA and X-ray diffraction (XRD). The results showed that KCC-1@ZIF-8 exhibited a significant increase in the BET surface area and pore size compared to the individual components KCC-1 and ZIF-8. These improved properties of the composite material were beneficial for enhancing the adsorption capacity. The effects of initial concentrations, solution pH and reaction time on the adsorption capacity were investigated. The adsorption kinetics and isothermal data of ZIF-8 and KCC-1@ZIF-8 fitted well with pseudo-second-order and Langmuir isotherm models. The results of adsorption thermodynamics show that the adsorption process is spontaneous and endothermic. KCC-1@ZIF-8 exhibited a very high adsorption capacity (751.46 mg g-1) at an initial TC hydrochloride concentration of 80 mg L-1 in an aqueous solution at 301.15 K, and the value was higher than that of ZIF-8 (549.80 mg g-1) under the same conditions. KCC-1 exhibited a relatively lower capacity (37.860 mg g-1). Based on these findings, KCC-1@ZIF-8 was considered a promising adsorbent for the treatment of wastewater contaminated with TC hydrochloride. Additionally, the composite material, when combined with high-performance liquid chromatography (HPLC), could be used as a solid-phase extraction adsorbent for the adsorption of TC hydrochloride in animal foodstuff samples. The calibration curves showed a linear range of 20-500 μg L-1, and the recovery rate ranged from 85.216% to 90.717%. No one has made adsorbents with this new structure before, and KCC-1@ZIF-8 possessed excellent adsorption properties, which make it a potential candidate for environmental remediation and analytical applications involving TC hydrochloride.

Application of central composite design to optimization of Yellow Tartarazine and Methylene Blue environmentally clean adsorption by untreated walnut shells

Climate change poses a real threat to the water security by altering the precipitation patterns and other weather variables, desirability function (df) was used to determine the interactive effects and optimize with the Central Composite Design (CCD) of important variables such as initial dyes concentration (Co : 20–100 mg L–1), solution pH (1.5–11), temperature (20–60 °C) and adsorbent dosage (0.1–1.3 g L–1) for the removal of toxic Yellow Tartarazine (YT) and Methylene Blue (MB) onto Untreated Walnut Shells (UWS). The analysis of variance (ANOVA) was applied for the treatment of experimental data, fitted by a second-order polynomial equation and multiple regression analysis. The ideal conditions optimized according to the response surfaces are initial concentration (COyt = 60 mg L–1, pHYT = 1.5, DYT = 0.7 g L–1 and TYT = 40 °C for YT and (Co MB = 60 mL–1, pHMB = 8.5, DMB= 0.7 g L–1 and TMB = 40 °C for MB). Experimental confirmation allowed to accurately determine the maximum eliminations (76.15) for YT and (76.81%) for MB under optimal conditions. Several error analysis equations were used to measure the goodness of fit. Kinetic studies showed that the adsorption kinetic data are well modeled by a pseudo-second-order model. Among the different models used to fit the experimental isotherms, the Langmuir model gave the best correlation with capacities qmax of 55.55 and 50.00 mg/g, for YT and MB respectively at 40 oC. The effect of temperature on the adsorption isotherms allowed to arrive at the thermodynamic functions, the negative values of free energy ( ΔG°), enthalpy ( ΔH°) and entropy ( ΔS°) indicate a spontaneous and exothermic adsorption of physical nature, confirmed by the activation energy ( Ea) for both dyes. The elimination of pollutants by new-generation adsorbents has proven to be very effective by application of statistical methodology, Central composite design and the desirability function.

Degradation of humic acid by UV/PMS: process comparison, influencing factors, and degradation mechanism.

In natural water bodies, humic acid (HA), generated during the chlorination disinfection process at water treatment plants, can produce halogenated disinfection by-products, increasing the risk to drinking water safety and posing a threat to human health. Effectively removing HA from natural waters is a critical focus of environmental research. This study established a synergistic ultraviolet/peroxymonosulfate (UV/PMS) system to remove HA from water. It compared the efficacy of various UV/advanced oxidation processes (AOPs) on HA degradation, and assessed the influence of different water sources, initial pH, oxidant concentration, and anions (HCO3 -, Cl-, NO3 -) on HA degradation. The degradation mechanism of HA by the UV/PMS process was also investigated. Results showed that under the conditions of 3 mmol L-1 PMS concentration, 10 mg L-1 HA concentration, initial solution pH of 7, and a reaction time of 240 minutes, the mineralization rate of HA by UV/PMS reached 94.15%. The pseudo-first-order kinetic constant (k obs) was 0.01034 and the single-electric energy (EE/O) was 0.0157 kW h m-3, indicating superior HA removal efficiency compared to other systems. Common anions (HCO3 -, Cl-, NO3 -) in water were found to inhibit the degradation of HA, and acidic conditions were more conducive to HA removal, with the optimal pH being 3. Free radical quenching experiments showed that both sulfate radical (SO4 -˙) and hydroxyl radical (˙OH) radicals were involved in HA degradation, with SO4 -˙ being the primary oxidant and ˙OH as the auxiliary species. Analyses using 3D-excitation-emission matrix (EEM), parallel factor analysis (PARAFAC), specific fluorescence index, and absorbance demonstrated that UV/PMS technology could effectively degrade HA in water. This study provides theoretical references for further research on the removal of HA and other organic substances using UV/PMS technology.

Construction of core-shell magnetic metal-organic framework composites Fe3O4@MIL-101(Fe, Co) for degradation of RhB by efficiently activating PMS.

Low catalytic efficiency and catalyst recovery are the key factors limiting the practical application of advanced oxidation processes. In this work, a core-shell magnetic nanostructure Fe3O4@MIL-101(Fe, Co) was prepared via a simple solvothermal method. The core-shell structure and magnetic recovery performance were characterized by various technologies. The results of dye degradation experiments proved that within 10 minutes, the Fe3O4@MIL-101(Fe, Co)/PMS system can degrade more than 95% of 10 mg per L Rhodamine (RhB) at an initial pH of 7, which possesses higher catalytic activity than the Fe3O4/PMS system and the MIL-101(Fe, Co)/PMS system. The effects of initial solution pH and coexisting anions in water on the degradation of RhB were further discussed. The results showed that Fe3O4@MIL-101(Fe, Co) displayed excellent degradation efficiency in a wide pH range of 3-11 and capability of resisting coexisting anions. It is worth mentioning that after five cycles, the RhB removal rate can still be maintained at over 90% after 10 minutes of reaction. Free radical quenching experiments were further studied, confirming that ˙OH and SO4-˙ were involved in the degradation of RhB, while the dominating active free radical was SO4-˙. The possible reaction mechanism of the RhB degradation process was also inferred.

Initial solution pH value for the construction of a 3D hydroxyapatite via the trisodium citrate-assisted hydrothermal route.

In this study, a trisodium citrate (TSC)-assisted hydrothermal method is utilized to prepare three-dimensional hydroxyapatite (3D HA). Understanding the role of TSC in the preparation of 3D HA crystals may provide valuable methods to design advanced biomaterials. As one of the indexes of solution supersaturation, the initial pH (ipH) value can not only directly affect the nucleation rate, but also affect the growth of HA crystals. In this work, the effect of the ipH on the microstructure, particle size distribution, and specific surface area of the 3D HA is explored. Results showed that the morphology of 3D HA transformed from a bundle to a dumbbell ball and then a dumbbell with an increase in the ipH. A corresponding mechanism of such a structural evolution was proposed, providing inspiration for the fabrication of innovative 3D HA structures with enhanced biological functionality and performance.

Copper(II) ion removal from aqueous solutions using alginate nanoparticles/ carboxymethyl cellulose/ polyethylene glycol ternary blend: Characterization, isotherm and kinetic studies

This study addresses the critical issue of removing copper(II) ions from water using an eco-friendly approach with natural biomaterials. Alginate, a natural polysaccharide, is employed as the primary adsorption material. The study involves the conversion of alginate into nanoparticles, and a ternary blend is prepared by mixing alginate nanoparticles with carboxymethyl cellulose and polyethylene glycol (AL-NPs/CMC/PEG). The blend's morphological and structural transformations have been comprehensively investigated using techniques such as DLS, FT-IR, XRD, TGA, and SEM. Batch experiments were conducted systematically to investigate crucial parameters, such as contact time (60–300 min), initial copper concentration (62.5 ppm–1000 ppm), solution pH (2–8), and adsorbent dosage (1–5 g). The results obtained are highly encouraging, revealing an impressive 80.9 % efficiency in the removal of copper ions. The acquired experimental data were then subjected to analysis with Langmuir and Freundlich, isotherm, as well as pseudo-first and pseudo-second-order kinetics studies. The outcomes from these isotherm and kinetics models indicated a favorable fit with the Freundlich isotherm, suggesting a strong affinity between the adsorbent and the metal ions. Furthermore, the kinetic studies revealed that the adsorption process closely adheres to pseudo-second-order kinetics, underlining the efficiency and reliability of the adsorption process. From desorption studies, 0.1 M HCl was an extremely effective eluant when compared to HNO3 and EDTA. It could be reused three time with appreciate efficiency. The research underscores the potential for an environmentally sustainable solution to address the persistent environmental challenge posed by copper ion contamination.

Kinetic Modeling of Electromembrane Extraction of Copper using a Novel Electrolytic Cell Provided with a Supported Liquid Membrane

The aim of this study is to investigate the kinetics of copper removal from aqueous solutions using an electromembrane extraction (EME) system. To achieve this, a unique electrochemical cell design was adopted comprising two glass chambers, a supported liquid membrane (SLM), a graphite anode, and a stainless-steel cathode. The SLM consisted of a polypropylene flat membrane infused with 1-octanol as a solvent and bis(2-ethylhexyl) phosphate (DEHP) as a carrier. The impact of various factors on the kinetics constant rate was outlined, including the applied voltage, initial pH of the donor phase solution, and initial copper concentration. The results demonstrated a significant influence of the applied voltage on enhancing the rate of copper mass transfer across the membrane. As the applied voltage increased, the rate constant also increased. Additionally, increasing the pH of the solution led to an initial elevate in the rate constant, reaching a maximum value at pH 5, after which it started to decline. Moreover, higher initial copper concentrations had an adverse effect on the rate constant. Notably, the concentration decay profiles observed under different operating conditions followed first-order kinetics, with correlation coefficients exceeding 0.99. The elucidation of this discovery emanated from a remarkable and striking congruence between the experimental data and the mathematical underpinnings of the first-order kinetics model. This serendipitous alignment profoundly reinforced the robustness, veracity, and unwavering reliability of meticulously obtained results, amplifying the credibility and trustworthiness of the present comprehensive study.

Accelerated iron valence cycling in Fenton system using activated hydrogen enhanced by MIL-100(Fe) modified by nano-Pd0 Particle.

In this paper, a novel Fenton reaction system which was called MHACF-MIL-100(Fe) was constructed. In this system, based on active hydrogen-accelerated FeIII reduction, the hydroxyl radical was continuously produced with a trace amount of total iron. The MIL-100(Fe) modified with the nano-Pd0 particle could be used to activate the H2. Under normal temperature and pressure, the target organic pollutants, such as sulfamethazine and 4-chloro phenol, could be degraded fast. In the condition of initial aqueous solution pH 3, 2 g L-1 dosage of MIL-100(Fe) catalyst loaded with nano-Pd0, Pd/MIL-100(Fe), 20 mM 30 wt% hydrogen peroxide, 25 μM ferrous chloride and 60 mL H2 min-1, 97.8% of sulfamethazine and 100% 4-chloro phenol could be degraded within only 5 min, respectively. Although the surface of the catalyst exhibited more obvious defects and roughness after 5 consecutive destructive experiment cycles, its basic structure could be maintained. The removal efficiency could be maintained at least more than 79% (sulfamethazine) and 94% (4-chloro phenol). That may be mainly attributed to the degradation of hydroxyl radical.

Functionalized magnetic chitosan-based adsorbent for efficient tetracycline removal: Deep investigation of adsorption behaviors and mechanisms

As removal performance of tetracyclines in traditional wastewater treatment plants cannot satisfy the increasingly strict discharge requirements, developing an efficient approach to overcome this problem is quite urgent. Herein, a novel functionalized magnetic chitosan-based adsorbent (Fe3O4@CAA) with core-shell structure and unique magnetic responsiveness was facilely prepared by ultrasound-initiated radical grafting copolymerization and cross-link reaction. The as-prepared Fe3O4@CAA was fully characterized with TEM, SEM, BET, FTIR, TGA, XRD, VSM, and served as an efficient adsorbent for tetracycline hydrochloride (TCH) removal. Adsorption behaviors of TCH by Fe3O4@CAA were deeply evaluated at different adsorption time, initial TCH concentration, reaction temperature, solution pH, and background pollutant concentration. Results showed that Fe3O4@CAA presented a more competitive adsorption capacity of 325.04 mg g−1 compared with Fe3O4@CS and other reported adsorbent, due to the introduction of more active adsorption sites by abundant functional groups, including amino groups, hydroxyl groups, and sulfonic acid groups. After saturated adsorption, TCH loaded Fe3O4@CAA was easily collected by magnetic separation, and recycled after acid pickling. Fe3O4@CAA was successfully reused in five adsorption-desorption cycles, without obvious adsorption capacity loss. In binary pollutant systems, inorganic cations and Pb(II) restrained TCH adsorption by competitive effect, while proper amount of Cu(II) promoted TCH adsorption by bridge effect. FTIR and XPS analyses revealed that the adsorption mechanism of TCH by Fe3O4@CAA mainly included electrostatic interaction and hydrogen bonding, and Cu(II) could play a “mediator” role to form a strong Cu(II)-TCH complex to enhance TCH removal performance. This study provides an effective strategy for the design of magnetic chitosan-based adsorbents and valuable guidance for the removal of tetracyclines from wastewater.

Design of a novel magnetic composite catalyst with highly efficient cobalt circulation for activating peroxymonosulfate to degrade tetracycline

In this study, a magnetic CoFe2O4/Co2O3/Na-X Zeolite (CFCOZ) composite catalyst was prepared via a co-precipitation hydrothermal method. Comprehensive characterizations suggest that the porous shell layer composed of CoFe2O4 and Co2O3 nanoparticles is evenly supported on Na-X zeolite. The specific surface area of CFCOZ is 266.93 m2/g. CFCOZ was exploited to catalyze peroxymonosulfate (PMS) to degrade tetracycline (TC). Catalytic degradation experiments indicated that the TC removal rate in the PMS/CFCOZ system was higher than that in the CoFe2O4/zeolite/PMS oxidation system. The highest degradation rate reached 96.6 % ([PMS] = 1 mM, 0.2-g/L CFCOZ, [TC] = 20 mg/L, initial pH = 7, room temperature). Several influence factors were investigated, including initial solution pH, PMS concentration, and CFCOZ dosage, etc. on the TC degradation. Electron paramagnetic resonance spectroscopy and reactive species scavenging experiments showed that 1O2, SO4−, and O2− played the predominant role in the TC removal. The possible catalytic degradation mechanism was proposed. It is found that CoFe2O4 and Co2O3 could synergistically activate PMS, and enhance the circulation efficiency between Co2+ and Co3+ to promote the generation of ROS. The cyclic experiments and characterization results between the fresh and the used CFCOZ showed its continuous catalytic activity and good structural stability.

Sea Urchin-like NiCo2O4 Catalyst Activated Peroxymonosulfate for Degradation of Phenol: Performance and Mechanism.

How to efficiently activate peroxymonosulfate (PMS) in a complex water matrix to degrade organic pollutants still needs greater efforts, and cobalt-based bimetallic nanomaterials are desirable catalysts. In this paper, sea urchin-like NiCo2O4 nanomaterials were successfully prepared and comprehensively characterized for their structural, morphological and chemical properties via techniques, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), among others. The sea urchin-like NiCo2O4 nanomaterials exhibited remarkable catalytic performance in activating PMS to degrade phenol. Within the NiCo2O4/PMS system, the removal rate of phenol (50 mg L-1, 250 mL) reached 100% after 45 min, with a reaction rate constant k of 0.091 min-1, which was 1.4-times higher than that of the monometallic compound Co3O4/PMS system. The outstanding catalytic activity of sea urchin-like NiCo2O4 primarily arises from the synergistic effect between Ni and Co ions. Additionally, a comprehensive analysis of key parameters influencing the catalytic activity of the sea urchin-like NiCo2O4/PMS system, including reaction temperature, initial pH of solution, initial concentration, catalyst and PMS dosages and coexisting anions (HCO3-, Cl-, NO3- and humic acid), was conducted. Cycling experiments show that the material has good chemical stability. Electron paramagnetic resonance (EPR) and quenching experiments verified that both radical activation (SO4•-, •OH, O2•-) and nonradical activation (1O2) are present in the NiCo2O4/PMS system. Finally, the possible degradation pathways in the NiCo2O4/PMS system were proposed based on gas chromatography-mass spectrometry (GC-MS). Favorably, sea urchin-like NiCo2O4-activated PMS is a promising technology for environmental treatment and the remediation of phenol-induced water pollution problems.

Role of Interface of Metal-Organic Frameworks and Their Composites in Persulfate-Based Advanced Oxidation Process for Water Purification.

The persulfate activation-based advanced oxidation process (PS-AOP) is an important technology in wastewater purification. Using metal-organic frameworks (MOFs) as heterogeneous catalysts in the PS-AOP showed good application potential. Considering the intrinsic advantages and disadvantages of MOF materials, combining MOFs with other functional materials has also shown excellent PS activation performance and even achieves certain functional expansion. This Review introduces the classification of MOFs and MOF-based composites and the latest progress of their application in PS-AOP systems. The relevant activation/degradation mechanisms are summarized and discussed. Moreover, the importance of catalyst-related interfacial interaction for developing and optimizing advanced oxidation systems is emphasized. Then, the interference behavior of environmental parameters on the interfacial reaction is analyzed. Specifically, the initial solution pH and coexisting inorganic anions may hinder the interfacial reaction process via the consumption of reactive oxygen species, affecting the activation/degradation process. This Review aims to explore and summarize the interfacial mechanism of MOF-based catalysts in the activation of PS. Hopefully, it will inspire researchers to develop new AOP strategies with more application prospects.

Enhanced removal efficiency of nitrogen and phosphorus from swine wastewater using MgO modified pig manure biochar

Pig manure and swine wastewater from livestock and poultry contain high levels of nitrogen and phosphorus, which can seriously threaten ecosystems. In this study, biochar derived from pig manure (PMBC) was modified by various magnesium salts to obtain pig manure biochar modified with MgO (MgO-PMBC), Mg(OH)2 (Mg(OH)2-PMBC) and MgCl2 (MgCl2-PMBC), and their capacities of simultaneous adsorption of NH4+-N and PO43--P were investigated. Results showed that the adsorption quantities for NH4+-N and PO43--P decreased in the order: MgO-PMBC >Mg(OH)2-PMBC > MgCl2-PMBC > PMBC. When the optimal dosage for MgO-PMBC was determined to be 0.6 g/L and the initial solution pH was set to the ideal value of 7, the maximum adsorption quantities for NH4+-N and PO43--P by MgO-PMBC reached 122.01 mg/g and 206.85 mg/g, respectively, which were 49.8 and 85.5 times of those of the PMBC. The specific surface area and total pore volume of MgO-PMBC were 9.4 times and 4.1 times of the PMBC. Removal rate of PO43--P from swine wastewater was 97.57%, and the concentration of PO43--P from treated swine wastewater was lower than 0.5 mg/L, the primary discharge standard of China’s Comprehensive Wastewater Discharge Standard. The enhanced simultaneous adsorption of NH4+-N and PO43--P by modified PMBC (MgO-PMBC) was ascribed to its greater specific surface area and total pore volume, and the reaction of crystallisation of struvite. Our results demonstrated that pig manure biochar modified by MgO can be used to treat swine wastewater effectively.