The development of energy-efficient amine-based absorbents is crucial for advancing industrial-scale CO2 capture. This study presents the alkylated ethylenediamine-based absorbents for CO2 capture and systematically investigates their structure–activity relationships. The findings reveal that increasing the degree of alkylation enhances the electron density around the primary amine groups, therefore strengthening their binding affinity towards CO2. Theoretical calculations further elucidate that functionalizing ethylenediamine with isopropyl groups can reduce the reaction energy barrier, consequently facilitating the CO2 absorption rate. Moreover, higher degrees of alkylation introduce stronger steric hindrance, promoting carbamate decomposition and enhancing CO2 cyclic capacity and desorption rates while reducing regeneration energy consumption. This work provides valuable insights into the structural design of amine absorbents with enhanced CO2 capture efficiency.

In order to improve the treatment of water produced from gas fields, it is necessary to clarify the main reasons for the emulsion stability of the produced water. In this work, 11 factors were selected, including the standing time, salinity, water-phase pH value, foaming agents in the produced water, corrosion inhibitors, defoamers, etc. The turbidity of the emulsion, zeta potential, average droplet size, and oil-water interfacial tension were used as evaluation indicators. The influences of different factors on the emulsion stability of the water produced from gas fields were studied from a macroscopic perspective, and it was identified that the foaming agent, corrosion inhibitor, and salinity were the key controlling factors. Molecular dynamics was used to simulate and study the morphology, relative concentration distribution, interfacial formation energy, and mean square displacement of a water-condensate oil-water system and a condensate oil-foaming agent-water system at each stage of the dynamic process, achieving the microscopic visualization of the oil-water interface and revealing the microscopic mechanisms by which the foaming agent and corrosion inhibitor promote emulsification at the molecular scale. The results show that combining research methods involving macroscopic experiments and microscopic simulations can more comprehensively and deeply clarify the emulsion stability of the water produced from gas fields, providing a scientific basis and technical reference for the design and selection of efficient water treatment agents.

This study addresses the preparation of heterogeneous catalysts for advanced oxidation processes and the construction of a corresponding catalytic oxidation system. A magnetic CoFe2O4@N–C catalyst, in which CoFe2O4 was partially coated with nitrogen-doped carbon (N–C), was prepared by a two-step high-temperature calcination method. The optimized preparation parameters were as follows: CoFe2O4 was prepared at a molar ratio of Co: Fe: citric acid: melamine = 1:2:0.6:0.6 and calcined at 600°C for 2 h. Subsequently, CoFe2O4 and melamine were mixed and ground at a mass ratio of 1:2, followed by calcination at 550°C for 2 h in a muffle furnace. The optimized oxidation system used 100 mg/L CoFe2O4@N–C as the catalyst and 0.5 mM peracetic acid (PAA) as the oxidant, and it was applied to simulated dye wastewater and comprehensive wastewater from an actual chemical industrial park. The degradation efficiencies for the cationic dyes (RhB and MB) and anionic dyes (MO and EBT) in the CoFe2O4@N–C + PAA catalytic oxidation system were 92.95%, 42.63%, 42.23%, and 95.79%, respectively. GC-MS analysis of water samples collected before and after treatment of the comprehensive wastewater from the chemical industrial park indicated that alkane components were completely or partially removed after the reaction. These results indicate that the constructed catalytic oxidation system has good treatment capacity for comprehensive wastewater from the chemical industrial park and can oxidatively degrade organic components in wastewater.

The effective treatment of fracturing flowback fluid, the volume of which has increased sharply with the widespread use of hydraulic fracturing, remains a major environmental and engineering challenge. This is due mainly to guar gum, a natural polymer with strong viscosity-enhancing capacity and high chemical stability, which makes the flowback fluid resistant to conventional treatment. To address this issue, this study investigated the catalytic oxidative degradation of guar gum. A CuFe2O4@montmorillonite (MMT) composite catalyst was synthesized via a citric acid-assisted sol-gel method, using MMT as a structural support. The resulting catalyst was employed to activate peroxymonosulfate (PMS) for the targeted degradation of guar gum. The effects of key operational parameters, including catalyst dosage, initial pH, reaction temperature, reaction time, initial guar gum concentration, and common coexisting ions, were systematically evaluated. Under the optimized conditions of 35 degrees C, 1000 mg L-1 guar gum, 500 mg L-1 PMS, and 100 mg L-1 catalyst, the viscosity reduction rate reached 95.96% after 2 h. Quenching experiments combined with electron paramagnetic resonance (EPR) analysis identified hydroxyl radicals (center dot OH), sulfate radicals (SO4 center dot-), and singlet oxygen (1O2) as the predominant reactive oxygen species responsible for degradation. X-ray photoelectron spectroscopy (XPS) analysis further revealed that synergistic electron transfer between surface Fe3+/Fe2+ and Cu2+/Cu+ redox couples facilitates efficient PMS activation. Moreover, the CuFe2O4@MMT/PMS system maintained strong degradation performance, with a viscosity reduction rate above 90%, across an initial guar gum concentration range of 100-2000 mg L-1. Notably, the catalyst retained high activity after seven consecutive reuse cycles, highlighting its excellent stability, environmental adaptability, and promising potential for practical application.

In this study, a novel peroxymonosulfate-based deep oxidation process (MnFe2O4@NBC/HA/PMS) was constructed using hydroxylamine (HA) as a reductant and nitrogen-doped biochar-loaded iron-manganese bimetallic material (MnFe2O4@NBC) as a catalyst to achieve efficient degradation of naphthalene (NAP). Under optimal conditions, the MnFe2O4@NBC/HA/PMS process removed 91.05 % of NAP after 120 min. Considerably contribution was observed from center dot OH and SO4 center dot-to removing NAP. Both laboratory results and theoretical calculation (density functional theory, DFT) jointly indicated that HA substantially enhanced the elimination efficacy of organic contaminants in wastewater. HA enhanced both the adsorption rate of MnFe2O4@NBC and the rate of utilization of PMS, while promoting the Fe2+/Fe3+ and Mn2+/Mn3+ turnover rate on the composite materials surface, thereby boosting the production of center dot OH and SO4 center dot-. The MnFe2O4@NBC/HA/PMS process effectively treated real wastewater, with MnFe2O4@NBC retaining high NAP degradation efficiency over multiple cycles. This study introduces a novel approach for degrading emerging pollutants in water and highlights the environmental applications of biochar-based composites.

The greenhouse gas CO2 is used as a precipitant to deharden the deep coalbed methane produced water (PW), allowing it to meet the reuse requirements. The pH of PW is the key factor affecting the absorption and dissolution of CO2. High raw water pH leads to higher CO2 absorption, callback pH, and CO(3)(2 )release. The aeration rate and aeration time determine how quickly and how much CO2 is absorbed and dissolved. Increasing temperature enhances the removal effect. Smaller CO2 bubble facilitates more rapid CO2 absorption, and high CO2 gas pressure increases the final CO2 dissolution. Under normal temperature and pressure, the pH of raw water is adjusted to 11, with an aeration rate of 200 mL/min for 16 min. In addition, the callback pH is equal to 12.80, resulting in a final dehardening effect of 99.77 %, making the treated PW suitable for reuse. Mechanistic studies have shown that at the first level of dehardness, CO2 is not dissolved enough under constant pressure, causing some Ca2+ to precipitate as Ca(OH)(2), which enhances hardness removal. To improve the dehardening effect, excessive callback pH can be used, and multi-stage dehardening ensures that Ca2+ precipitates as CaCO3. Meanwhile, Mg2+ is predominantly removed as Mg(OH)(2) in the first stage. Dehardening can produce small CaCO3 microsphere by-products, which can be considered for further recycling. The cost of CO2 as a dehardening agent is 23.83% better than Na2CO3, which not only achieves the dehardening of deep coalbed methane PW at a low cost, but also provides a feasibility reference for the early realization of the "dual carbon" target to a certain extent.

The incorporation of ZIF-67 into hydrogels for wastewater pollutant remediation has been widely studied, but the synthesis often requires organic solvents such as methanol or ethanol, which can result in the generation of toxic liquid waste. In this study, a novel hydrogel (ZIF-67@SL) was synthesized by integrating ZIF-67 into a dual- network system of sodium lignosulfonate (SL) and acrylamide (AM) using an in situ precipitation method in water. The material was characterized by XRD, FTIR, XPS, SEM, TEM, BET, and TGA analyses. ZIF-67@SL was used to activate peroxymonosulfate (PMS) for degrading naphthalene (NAP) in aqueous solutions. Results showed that ZIF-67@SL effectively activated PMS, achieving an 85.43 % removal rate of NAP within 60 min at 30 degrees C, with an initial NAP concentration of 10 mg center dot L-1, ZIF-67@SL dosage of 800 mg center dot L-1, PMS concentration of 1000 mg center dot L-1, and pH 7.0. The catalytic efficiency remained high after five recycling cycles. Quenching experiments and EPR spectra revealed that the degradation of NAP in the ZIF-67@SL/PMS system occurred through both free radical pathways (SO4 center dot-, center dot OH, and O-2(center dot-)) and a non-radical pathway (O-1(2)). XPS analysis indicated that the activation of PMS and generation of radicals were influenced by Co2+, Co3+, Co-0, nitrogen elements, and adsorbed oxygen in the ZIF-67@SL composite. Furthermore, the ZIF-67@SL/PMS system demonstrated strong resistance to low-concentration anions and humic acid (HA) interference and effectively removed multiple polycyclic aromatic hydrocarbons (PAHs) in mixed wastewater. Maximum removal rates for NAP, ACN, ACT, PHE, and FLU were 95.26 %, 99.9 %, 99.79 %, 99.04 %, and 75.69 %, respectively. This study provides an environmentally friendly strategy for wastewater treatment by synthesizing ZIF-67 hydrogel in water and utilizing it as an efficient catalyst.

To achieve efficient activation of peracetic acid (PAA) for degrading refractory organic pollutants, a highly active magnetic nitrogen-doped carbon partially covered catalyst, CoFe2O4@N - C, was successfully synthesized. An advanced oxidation system based on CoFe2O4@N - C/PAA was constructed, consisting of 0.5 mM PAA and 100 mg/L CoFe2O4@N - C. The system exhibited good pH adaptability and achieved a degradation rate exceeding 98 % for Rhodamine B (RhB) wastewater at concentrations ranging from 50 mg/L to 300 mg/L. Higher temperatures resulted in improved degradation efficiency. The system demonstrated strong resistance to interference; HCO3-, CO32-, and H2PO4- inhibited degradation, whereas Fe3+, Co2+, and Cu2+ enhanced it. Cl-, NO3-, SO42-, Mn2+, Ca2+, and Mg2+ showed minimal effect. This system effectively degraded pollutants in various water environments. CoFe2O4@N - C retained 39.91 % degradation efficiency after four cycles, with the RhB degradation rate reaching 89.20 % following regeneration, and an average recovery efficiency of 87.18 %. Mechanistic studies revealed that the catalytic active center of CoFe2O4@N - C was primarily CoFe2O4, with the reactive oxygen species (ROS) generated by the system predominantly comprising 1O2 and O2 center dot- , while center dot OH and R - O center dot were also present. These ROS preferentially attacked the benzene ring structure, as well as N and O sites of RhB. The degradation pathway of RhB primarily comprises de-ethylation and deamination, destruction of the oxanthene chromophore, oxidation and cleavage of aromatic structures containing benzene rings, and subsequent gradual mineralization into H2O and CO2. After treatment, the biological toxicity of RhB wastewater was significantly reduced. This work provides a practical strategy for developing efficient heterogeneous catalysts and PAA-based advanced oxidation processes for pollutant remediation.

The conversion of agricultural biomass waste into biochar-based value-added catalysts has received great attention. In this study, Ni-Cu@BC composite catalyst was prepared by impregnation pyroptosis using the walnut shell (BC) as carrier and transition metal nickel and copper oxide as active components. The synthesized samples were characterized using FT-IR, XRD, SEM&EDS, BET, and XPS techniques. The prepared Ni-Cu@BC catalyst was subsequently employed to activate sodium hypochlorite (NaClO) for the catalytic degradation of crystal violet (CV). The effect of raw material ratio (Ni/BC), metal ratio (Ni/Cu), effective chlorine concentration, catalyst dosage, pH, temperature, initial concentration of CV and interfering ions on the removal effect of CV during the preparation process was investigated, and the oxidative degradation mechanism and application potential of this system were explored. The results showed that the activated NaClO was the best when Ni/BC mass ratio was 1:1 and Ni/Cu mass ratio was 5:1. When the reaction temperature was 20 degrees C, the initial CV concentration of 100 mg/L, the initial pH of 4.0, the initial effective chlorine concentration of 1.52 %, and the catalyst addition of 0.5 g/L, the decolorization rates of CV, MB, RhB and MO could reach 98.89 %, 85.06 %, 99.00 % and 88.00 % respectively at 30 min. CV degradation process meets the quasi-primary kinetics, and the reaction rate constant was 0.1474 min(-1). The quenching experiments and EPR spectra show that the active species produced in the Ni-Cu@BC/NaClO system were mainly OCl center dot, center dot OH, O-1(2) and O-2(-center dot), and the catalytic degradation of CV was achieved through the synergistic action of free radical degradation pathway (center dot OH, O-2(-center dot) and OCl center dot) and non-free radical degradation pathway (O-1(2)). XPS analysis showed that the metals in Ni-Cu@BC catalyst mainly exist as NiO, CuO and Cu2O, realizing the redox cycle of Ni2+/Ni3+/ Ni2+, Cu+ gradually transforms into Cu2+, C-O and CO transform into C-C/C-H, and lattice oxygen and adsorbed oxygen transform into surface hydroxyl groups, promoting the electron transfer of the reaction system and the generation of reaction active sites. The order of inhibitory effects of common inorganic anions and organic matter (HA) on CV removal was HCO3-> NO3-> HA > Cl-> SO42-> HPO42-, and found that the catalytic system has strong anti-interference ability on Cl-, SO42- and HPO42-. It was suggested that the actual treatment of CV dye wastewater can remove HCO3- and NO3- in advance, while HCO3- only shows a more significant inhibitory effect when the concentration was greater than 200 mM. In addition, the chelating agent sodium citrate and the initial concentration of CV in printing and dyeing auxiliaries can also affect the decolorization reaction of CV, and the inhibitory effect increases with the increase of concentration. After five Ni-Cu@BC catalyst cycle experiments, the CV decoralization rate was still higher than 90 %, and the Ni and Cu metal ions were leached least at concentrations of 0.24 mg/L and 0.13 mg/L, respectively, indicating that the catalyst has good reusability and great potential for application.

Gas production during the electrochemical treatment of waste liquids has potential safety risks. Herein, hydrogen (H-2) production in such treatment was taken as the control target. Electrode combinations with relatively low H(2)production were selected for electrochemical treatment during a fracturing flowback fluid experiment, in which mesh-like titanium-based ordinary ruthenium-iridium-palladium-coated electrode was the anode and plate-like titanium-based ordinary ruthenium-iridium-palladium-coated electrode was the cathode. The effects of electrolysis time (t), electrolytic current (I), electrode spacing (D), and other factors on H(2)production in the electrolytic process were investigated. On the basis of the experimental data, a model was established using the support vector machine (SVM) method. Firstly, the three parameters of the radial basis function kernel of the model were simultaneously optimized using the quantum-particle swarm optimization algorithm as follows: penalty parameter = 256, kernel parameter = 0.0097039, and loss parameter = 0.014928. Then, an SVM regression model was established according to the three optimal parameters. The correlation coefficient was 0.98291 (r= 0.9914), and the mean-square error was 1.1883. The regression model was used to predict the technological conditions (t, I, andD) for the maximum/minimum H(2)production in the electrochemical treatment of fracturing flowback fluid. The values weret= 50 min,I= 1.5 A, andD= 2.0 cm for the maximum H(2)production, andt= 30 min,I= 0.5 A, andD= 6.0 cm for the minimum H(2)production. Under these process conditions, the predicted maximum/minimum H(2)production volumes were 145.04 and 20.47 mL, respectively.

The conversion of agricultural biomass waste to value-added biochar (BC)-based catalysts receives tremendous interest because it falls under the resource recycle concept. In this work, a magnetic iron-manganese bimetallic catalyst (MnFe2O4@NBC) with nitrogen-doped BC as the carrier was prepared through the solvothermal method using agricultural waste walnut shells as the precursor. Moreover, the structure, morphology, and magnetic separation properties of the catalyst were comprehensively analyzed by various characterization methods. The prepared MnFe2O4@NBC catalyst was coupled with peroxymonosulfate (PMS) for oxidative degradation of naphthalene (NAP). Results showed that MnFe2O4@NBC could effectively activate PMS, and the removal rate of NAP could reach 80.17 % in 120 min. The degradation of NAP through the synergistic action of the free radical pathway (SO4 center dot- and center dot OH) and the nonradical pathway (O-1(2)), but the free radical pathway was dominant. XPS, electrochemical profiles, and DFT calculations confirmed that the catalyst surfaces of Fe2+, Mn2+, C=O, and pyridine nitrogen and the defective structures are important reaction sites for PMS activation; the synergistic effect of Fe and Mn bimetals promotes the rapid cycling of metal redox pairs, whereas NBC promotes the dispersion of MnFe2O4, the direct activation of PMS, the enhancement of electron transfer, and the formation of a built-in electric field to facilitate the activation process. The catalysts showed a decrease in the removal of NAP after three times of reuse, but their activity could be restored by simple heat treatment, thus showing great potential for application. In brief, this work provides an efficient MnFe2O4@NBC heterogeneous catalyst and a new insight into PMS activation, which extends the potential application of BC-based catalysts for environmental remediation.

Catalytic oxidation processes have the significant advantage of fast and efficient removal of refractory organic matter, including radical and non-radical pathways, and the active species play a critical role in this process. Detecting these active species quickly and accurately is of utmost importance. Such detection not only aids in optimizing the catalytic oxidation process but also helps clarify the degradation mechanism of pollutants. However, detecting these active species has been a major difficulty. Existing detection technologies are primarily used for conventional free radicals, singlet oxygen, high-valent metals, and other active species. Most of these methods involve indirect detection, but they come with inevitable defects. Given the high activity and short lifespan of active species, detecting them directly, along with other unknown active species, poses significant challenges. This review systematically introduces the technical principles and application status of several main detection methods, analyzing the drawbacks and proposing solutions for each detection method. New methods such as EPR/ESR and XANES for the direct detection of active species and emerging organic free radicals are also mentioned. Finally, we propose the combination of different methods according to the specific requirements as the optimal approach for detecting active species in a catalytic oxidation system, enabling cross-confirmation of detection results.

Fluorescence spectroscopy is a powerful tool to determine polycyclic aromatic hydrocarbons (PAHs) owing to the strong endogenous fluorescence of these compounds. However, the presence of unknown interferences and overlapped spectra hinders the accurate determination of PAHs in oilfield produced water. Moreover, surfactants frequently coexist in oilfield produced water and will seriously affect the fluorescence signals of PAHs. Herein, a new methodology applying third-order calibration to process four-way (4D) fluorescence data was proposed to solve these problems and achieve accurate determination of pyrene, fluorene, phenanthrene, and fluoranthene as an example in oilfield produced water. The methodology is based on excitation-emission matrix fluorescence modulated by different concentrations of sodium dodecyl benzene sulfonate (SDBS) in the analyzed samples. The 4D fluorescence data were processed by third-order calibration methods including four-way parallel factor analysis (4-PARAFAC) and alternating weighted residue constraint quadrilinear decomposition (AWRCQLD), and the results were compared with those of second-order calibration methods. It was proved that third-order calibration was capable of accurately identifying and quantifying PAHs together with SDBS in oilfield produced water, which has better quantitative results and figures of merit compared to second-order calibration. This study provided a new approach to generating 4D fluorescence data and opened up an avenue for the accurate determination of PAHs in complex oilfield produced water with surfactants.

Nickel-iron bimetallic catalysts (Ni-Fe/Al2O3) with activated alumina as the carrier were prepared by impregnation pyrolysis, and the structure and morphology of the catalysts were analyzed by characterization via X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, programmed tem-perature rise reduction, and X-ray photoelectron spectroscopy. The prepared Ni-Fe/Al2O3 was used to catalyze sodium hypochlorite (NaClO) for oxidative degradation of methylene blue (MB). The effects of the dosage of iron nitrate in the preparation process and the catalyst dosage, effective chlorine concentration, pH, temperature, initial MB concentration, and coexisting ions on the MB removal effect in the oxidative degradation experiment were investigated. Then, the oxidative degradation mechanism and practical application prospects of the system were examined. Results showed that the Ni and Fe nitrate mass ratio of 5:1 was favorable for the dispersion of Ni elements in the catalyst preparation process. When the temperature was 45 degrees C, the initial concentration of MB was 50 mg/L, the dosage of Ni-Fe/Al2O3 was 20 g/L, the initial effective chlorine concentration was 1.76%, and the initial pH was 4.0. The removal rate of MB could reach 98.98% within 40 min, and the degradation process was in accordance with quasi primary kinetics, with reaction rate constant of 0.0873 min(-1). The experimental result of free radical quenching and electron paramagnetic resonance indicated that the addition of Ni-Fe/Al2O3 induced the decomposition of NaClO to produce a large amount of singlet oxygen (O-1(2)), O-1(2) and HOCl worked together to oxidatively degrade MB. Ni3+/Ni2+ redox cycles play an important role in activating HOCl to produce active species. The common inorganic anions (Cl-, NO3-, and SO42-) did not inhibit the removal of MB significantly, whereas humic acid showed a more significant inhibitory effect only at concentrations greater than 20 mg/L. In the five recycling experiments, the catalysts showed low metal leaching rate and high MB removal rate. Ni-Fe/Al2O3 was reusable, and it showed excellent application potential.

Heavy metal pollution is becoming increasingly serious. Heavy metal pollutants are nonbiodegradable and can be bioenriched through the food chain, and thus, they greatly threaten the environment and human health. Hydrogels, as an ideal adsorbent, have been widely used to treat heavy metal industrial wastewater. Sodium lignosulfonate hydrogel (LS) was prepared by free-radical grafting copolymerization, and nano-Fe3O4 particles were loaded in LS by an in-situ precipitation method (Fe3O4@LS). The magnetic properties and adsorption ca-pacity of Fe3O4@LS are closely related to the load capacity of Fe3O4. XRD, FTIR, XPS, SEM, TEM, BET, and TGA analyses of the materials were performed. Subsequently, the removal effect of the typical pollutant Cd2+ in heavy metal-polluted water was studied with Fe3O4@LS as the adsorbent. The influences of the Fe3O4@LS dosage and initial pH were investigated, and the adsorption kinetics and thermodynamics were further explored and dis-cussed. Finally, the adsorption mechanism of Fe3O4@LS on Cd2+ was obtained. Results show that Fe3O4@LS has a more stable spatial network structure than LS, and the pore size, specific surface area and active sites increase. The maximum adsorption capacity can reach 88.00 mg/g when pH = 6 and the dosage of Fe3O4@LS is 1000 mg/ L. The adsorption of Cd2+ by Fe3O4@LS conforms to pseudosecond-order kinetics and the Temkin isothermal adsorption model. Further mechanistic investigations show that the sorption of Cd2+ on Fe3O4@LS is mainly attributed to surface complexation, electrostatic attraction and coprecipitation. The coexistence of cations in water will inhibit the adsorption of Fe3O4@LS. Fe3O4@LS has superparamagnetism and a good response to an external magnetic field. The adsorption rate can still reach >60 % after four elutions with NaCl as the eluent. This material can be reused and has good application potential.

Petroleum-containing substance (PCS) is a general term used for petroleum and its derivatives. A comprehensive characterization of PCSs is crucial for resource exploitation, economic development and environmental protection. Fluorescence spectroscopy, especially excitation-emission matrix fluorescence (EEMF) spectroscopy, has been proved to be a powerful tool to characterize PCSs since its remarkable sensitivity, selectivity, simplicity and high efficiency. However, there is a lack of systematic review focusing on this field in the literature. This paper reviews the fundamental principles and measurements of EEMF for characterizing PCSs, and makes a systematic introduction to various information mining methods including basic peak information extraction, spectral parameterization and some commonly used chemometric methods. In addition, recent advances in applying EEMF to characterize PCSs during the whole life-cycle process of petroleum are also revisited. Furthermore, the current limitations of EEMF in the measurement and characterization of PCSs are discussed and corresponding solutions are provided. For promoting the future development of this field, the urgent need to build a relatively complete EEMF fingerprint library to trace PCSs, not only pollutants but also crude oil and petroleum products, is proposed. Finally, the extensions of EEMF to high-dimensional chemometrics and deep learning are prospected, with the expectation of solving more complex systems and problems.

In this work, data from experiments concerning carbon components in various forms, including graphite, graphene oxide (GO), active carbon, compilations, and analyses of the substances used as efficient wastewater management agents, are conducted. The initial phase involved characterizing the mentioned carbon compounds and nanoparticles (NPs) using various complementary methods. Raman spectrophotometry, energy-dispersive spectroscopy, scanning electron microscopy, and zeta spectrum research are involved in the approach. The next obstacle was coming up with a very straightforward procedure that would allow us to examine whether carbon NPs behaved in a mixture of effluent water and active sludge regarding hydrodynamic and physiological consequences. Principal component analysis (PCA) (univariate and multivariate) has confirmed the complicated relationships of NPs made of GO with organisms observed in processed wastewater. PCA techniques are used to evaluate experimental outcomes. Utilizing the results from this experiment, several huge-scale studies on how active NPs affect wastewater purification may be designed. Simulations using PCA clearly showed that GO significantly impacts the wastewater technical processes under investigation. It is envisaged that the discoveries will enable the design of clever conservation technologies.

A batch experiment was used in studying the effect of acrylic-acid-modified walnut shell (MWNS) as a low-cost adsorbent for removing Rhodamine B (RB) cationic dye in aqueous solutions. The adsorbent dosage, initial dye concentration, contact time, temperature, pH, and supporting electrolyte concentration on the adsorption behaviour of the adsorbent were explored. The adsorbent was characterized using the point of zero charge (pH(PZC)), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), automatic specific surface analysis (BET), and X-ray photoelectron spectroscopy (XPS). Results showed that MWNS had abundant active groups and rough surface, which is conducive to the adsorption process. The kinetics and equilibrium data of MWNS-to-RB adsorption were in accordance pseudo-second-order kinetic and Freundlich isotherm models, respectively. Under optimal adsorption conditions, the maximum adsorption capacity of RB was 48.87 mg center dot g(-1). Thermodynamic results showed spontaneously and exothermically the adsorption process. Moreover, the addition of electrolyte had a negative effect on equilibrium adsorption capacity and adsorption rate. HIGHLIGHTS Acrylic-acid-modified walnut shells was used as an adsorbent for the removal of Rhodamine B (RB). The adsorption of RB by modified walnut shells was greatly affected by pH. Pseudo-second-order kinetic and Freundlich model fit the experimental data. The modified walnut shell can remove RB through electrostatic attraction, hydrogen bonding, and electron donor-acceptor interaction.

ABSTRACT In the present study, we synthesized a cationic lignosulfonate hydrogel (LS-g-P (AM-co-DAC)) by grafting acrylamide (AM) and acryloxyethyl trimethyl ammonium chloride (DAC) onto sodium lignosulfonate (LS) via free radical copolymerization. The solution pH, contact time, initial concentration, and temperature were comprehensively investigated through the static adsorption method for the adsorption behaviours of Cr(VI) by the hydrogel. The experimental results show that the best conditions were a temperature of 30°C, a dosage of 0.1 g, pH = 3, a concentration of 50 mg / L, and contact time = 2 h with removal efficiencies of above 70% and adsorption capacity of 18.14 mg·g−1. The adsorption process followed the Langmuir isothermal model, indicating monolayer adsorption, and the maximum adsorption capacity was 58.86 mg·g−1. Adsorption kinetics results show that the pseudo-second-order kinetic model dominated the adsorption process, and the adsorption activation energy was 5.489 kJ·mol−1. In addition, the adsorption involved spontaneous exothermic and entropy reduction. The combination of FT-IR, SEM, and XRD was used to characterize the structure and properties of the prepared hydrogel, and the adsorption mechanism was the result of electrostatic attraction, physical and chemical adsorption, and hydrogen bond. The hydrogel has good regenerative properties after desorption. Overall, this work synthesized an environmentally friendly biomass lignin-based hydrogel, which can be used as an adsorbent for the treatment of anionic pollutants, and explored a new method for the high-value utilization of industrial lignin. Highlights Novel cationic lignosulfonate hydrogel (LS-g-P (AM-co-DAC)) was synthesized by a free radical method. SEM and XRD results confirmed the surface of the obtained hydrogel shows a 3D network structure and does not have a crystal structure. LS-g-P (AM-co-DAC) hydrogel adsorbent can selectively adsorb Cr6+ at pH 3.0. The adsorption conditions and the adsorption mechanism were studied in detail. Electrostatic interaction plays a key role in the adsorption of Cr6+. GRAPHICAL ABSTRACT