Increase In Initial Concentration Research Articles

Enhanced heavy metal adsorption capacity of surface-functionalized Philippine natural zeolite in simulated wastewater

The adsorption efficiency of surface-functionalized Philippine natural zeolite (PNZ) for heavy metal uptake from single and mixed metal ion-simulated wastewater solution is reported in this work. Atomic adsorption spectroscopy (AAS) findings revealed that NaCl-modified PNZ (MPNZ) exhibited the highest zinc ion adsorption of 99.96 % while PNZ yielded an adsorption of 95.61 %. The adsorption isotherms of raw PNZ and MPNZ both show similar shapes that reflect Type IV adsorption-desorption isotherms with Type H2 hysteresis loop which can be observed for micro-mesoporous materials (pore containing 2–50 nm). An increase in PNZ pore size from 10.11 nm to 13.36 nm for NaCl-PNZ and 15.59 for NaOH-PNZ is observed after alkaline treatment. EDS confirmed the decrease in Si/Al ratio from 4.02 to 3.76, indicative of possible higher negative charge in the PNZ framework which is favorable for an enhanced Coulombic or electrostatic interaction with the cationic heavy metals being detected in this study. MPNZ demonstrated an adsorption capacity of 99.96 % for copper in mixed-ion solution while 88.49 % and 86.67 % were obtained for zinc and nickel, respectively. These values are higher compared to PNZ having only 32.21 % uptake for zinc and 38.00 % for nickel. A hierarchy of the average metal adsorption capacity showed the order: copper > nickel > zinc. Rapid adsorption at the first hour of the adsorption reaction was attained in all solutions while samples with pH 9 exhibited the highest Ni2+ and Zn2+ percent removal. Moreover, the increase in initial solution concentration led to lower adsorption efficiency and the maximum uptake was attained at 100 ppm. The equilibrium data of adsorption and mechanism were suitably described by Langmuir isotherm model. With these, surface functionalization of PNZ has further enhanced its cationic adsorption capacity on heavy metals in both single and mixed-ion solution having promising potential for wastewater remediation.

Bioremediation of Wastewater Contaminated with Dyes, Rhodamine B Using Alginate Immobilized Cell of Spirulina platensis

Bioremediation of wastewater contaminated with rhodamine B dyes using alginate immobilized cell of Spirulina platensis was studied. Factors affecting the dye adsorption such as pH, contact time, adsorbent dose, and initial dye concentration were investigated. The results showed that the optimum pH for dye adsorption was at 2 with an adsorption capacity of 0.86±0.00 mg/g. The adsorption was very rapid and reached equilibrium within 180 min with an adsorption capacity of 1.24±0.00 mg/g. Dye adsorption capacity by this alga was reduced at high adsorbent dose whereas the increase of initial concentration of dye increased the adsorption capacity. The adsorption isotherm correlated with Langmuir with the maximum adsorption capacity (qm) of 52.70±3.18 mg/g. Adsorption kinetic correlated with pseudo-second order. The adsorption rate limiting step were film diffusion rate and secondary rate of intraparticle diffusion. This study suggested that alginate immobilized cell of S. platensis can be applied for treatment of wastewater contaminated with rhodamine B.

Statistical physics investigation on the simultaneous adsorption mechanism of Cd2+ and Pb2+ on amino functionalized activated carbon derived from coal gasification fine slag

In this study, a novel surface amino-functionalized activated carbon (T-AC) was synthesized from coal gasification fine slag (CGFS) and used as an adsorbent for heavy metal ions. T-AC exhibits excellent adsorption capacity for Cd2+ and Pb2+. The adsorption process of Cd2+ and Pb2+ onto T-AC was found to be spontaneous. The dominant adsorption process was chemisorption, primarily involving chelation and covalent bonding. In binary systems, as the initial concentration increases, the independent adsorption effect of Pb2+ and Cd2+ gradually becomes a competitive adsorption effect. Statistical physical models revealed that the adsorption of T-AC for Cd2+ and Pb2+ in single systems followed a multi-molecular adsorption process, whereas in binary systems, it involved a multi-anchorage process. The adsorption capacity was primarily influenced by the number of ions attached to the receptor sites and the density of the adsorbent receptor sites. Moreover, elevating temperature enhanced the thermal movement of heavy metal ions within the pore structure of the adsorbent, reducing their tendency to aggregate at the active sites. This work provides insights into the microscopic-level adsorption process of heavy metal ions by carbon-based materials and contributed to understand of the adsorption behavior.

Box-Behnken Design for Photocatalytic Degradation of Sudan Black B by Catalyst-Embedded Multiwalled Carbon Nanotubes

This research employs a Box Behnken design-based technique for photocatalytic use of Multiwalled Carbon Nanotubes (MWCNTs) derived from spray pyrolysis. This procedure was used for photocatalytic degradation applications on Sudan black dye using Citrus limonum oil as a carbon precursor and Fe/Co/Mo supported on silica as a catalyst. The influence of initial dye concentration was compared to the effects of H2O2, catalyst concentration and solar light intensity. The Response Surface Methodology was used to optimize growth parameters for higher yield and graphitization. The as-grown CNTs were exemplified using scanning and transmission electron microscopy and Raman spectroscopy. This work resulted in the identification of the optimal set of spray pyrolysis turning parameters for achieving high CNT yield and effective decolorization of Sudan black B dye by employing MWCNTs as catalyst. The degree of decolorization of Sudan black B dye increases upto a certain level with an increase in initial H2O2 concentration and subsequently declines as excess H2O2 hydroxyl radicals formed serve as scavengers, resulting in less dye decolonization.

Study on removal performance of Fe3+ by biomass-based activated carbon and Liquefaction of Poplar Sawdust catalyzed by ferro activated Carbon

The adsorption experiment of iron ions on biomass based nut shell activated carbon was conducted to explore the adsorption capacity of iron ions on biomass based activated carbon and the key influencing factors: pH value, initial concentration of solution and adsorption time on the adsorption effect of activated carbon. The preparation of supported catalyst of activated carbon iron and its influence on the effect of catalytic liquefaction of poplar sawdust were investigated. The results showed that the optimal pH value of Fe3+ solution adsorbed by activated carbon was 5.0. The adsorption rate of activated carbon decreased with the increase of initial ion concentration, and the adsorption equilibrium of activated carbon reached at 250min. The optimum concentration of poplar sawdust liquefaction catalyzed by iron supported on activated carbon is between 6mg/L and 10mg/L.

Degradation performance and mechanism of microcystins in aquaculture water using low-temperature plasma technology

The eutrophication of aquaculture water bodies seriously restricts the healthy development of the aquaculture industry. Among them, microcystins are particularly harmful. Therefore, the development of technologies for degrading microcystins is of great significance for maintaining the healthy development of the aquaculture industry. The feasibility and mechanism of removing microcystins-LR by dielectric barrier discharge (DBD) plasma were studied. DBD discharge power of 49.6 W and a treatment time of 40 min were selected as the more suitable DBD parameters, resulting in microcystin-LR removal efficiency of 90.4%. Meanwhile, the effects of initial microcystin-LR concentration, initial pH value, turbidity, anions on the degradation effect of microcystin-LR were investigated. The removal efficiency of microcystin-LR decreased with the increase of initial microcystin-LR concentration and turbidity. The degradation efficiency of microcystin-LR at pH 4.5 and 6.5 is significantly higher than that at pH 8.5 and 3.5. HCO3− can inhibit the removal efficiency of microcystin-LR. Furthermore, five intermediates products (m/z = 1029.5, 835.3, 829.3, 815.4, 642.1) were identified in this study, and the toxicity analysis of these degradation intermediates indicated that DBD treatment can reduce the toxicity of microcystin-LR. e－aq, •OH, H2O2, and O3 have been shown to play a major role in the degradation of microcystin-LR, and the contribution ranking of these active species is e－aq > •OH > H2O2 > O3. The application of DBD plasma technology in microcystin-LR removal and detoxification has certain development potential.

Competitive Adsorption of Cd(II) and Zn(II) on Biochar, Loess, and Biochar-loess Mixture

Combined heavy metal contamination in soil is a common phenomenon. Biochar amendment into the soil is considered to be an alternative for immobilization remediation of soil contaminated with heavy metals due to its adsorption and alkalization. However, much attention has been paid to the adsorption and immobilization of single heavy metals by biochar. In this paper, the competitive adsorption of Cd(II) and Zn(II) on biochar derived from cotton straw and pig manure at 500℃ (BCS500 and BPM500), loess and biochar-loess mixtures were investigated using the batch equilibrium method. The results showed that the adsorption capacities of biochars, loess, and biochar-loess mixtures to Cd(II) and Zn(II) in the mixed Cd-Zn systems increased with the increase of initial metal concentrations of Cd(II) and Zn(II). The adsorptive capacities of BCS500 and BPM500 to Cd(II) in mixed Cd-Zn system were 33% and 35% less than those in the single Cd(II)systems, while the adsorptive capacities to Zn(II) were 62% and 56% less than those in the single Zn(II) systems. The adsorptive capacities of loess to Cd(II) and Zn(II) in mixed Cd-Zn systems were 29% and 55% less than those in the single metal systems. The adsorptive capacities of loess-BCS500 (LBCS) and loess-BPM500 (LBPM) to Cd(II) in mixed Cd-Zn system were 40% and 38% less than those in the single Cd(II) systems, while the adsorptive capacities to Zn(II) were 63% and 60% less than those in the single Zn(II)systems. Moreover, the competitive adsorptive capacity of Cd(II) is greater than that of Zn(II). It can be seen that when heavy metal pollution with similar nature of multiple elements exists in soil, the amount of adsorbent should be increased to resist the possible weakened adsorption caused by competitive adsorption in order to guarantee an effective absorption treatment.

Influence of water chemistry and operating parameters on PFOS/PFOA removal using rGO-nZVI nanohybrid

Graphene and zero-valent-iron based nanohybrid (rGO-nZVI NH) with oxidant H2O2 can remove perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) through adsorption-degradation in a controlled aquatic environment. In this study, we evaluated how and to what extent different environmental and operational parameters, such as initial PFAS concentration, H2O2 dose, pH, ionic strength, and natural organic matter (NOM), influenced the removal of PFOS and PFOA by rGO-nZVI. With the increase in initial PFAS concentration (from 0.4 to 50 ppm), pH (3 to 9), ionic strength (0 to 100 mM), and NOM (0 to 10 ppm), PFOS removal reduced by 20%, 30%, 2%, and 6%, respectively, while PFOA removal reduced by 54%, 76%, 11%, and 33% respectively. In contrast, PFOS and PFOA removal increased by 10% and 41%, respectively, with the increase in H2O2 (from 0 to 1 mM). Overall, the effect of changes in environmental and operational parameters was more pronounced for PFOA than PFOS. Mechanistically, •OH radical generation and availability showed a profound effect on PFOA removal. Also, the electrostatic interaction between rGO-nZVI NH and deprotonated PFAS compounds was another key factor for removal. Most importantly, our study confirms that rGO-nZVI in the presence of H2O2 can degrade both PFOS and PFOA to some extent by identifying the important by-products such as acetate, formate, and fluoride.

Xylitol fermentation characteristics with a newly isolated yeast Wickerhamomyces anomalus WA

Xylitol is an increasingly popular functional food additive, and the newly isolated yeast Wickerhamomyces anomalus WA has shown extensive substrate utilization capability, with the ability to grow on hexose (d-galactose, d-glucose, d-mannose, l-fructose, and d-sorbose) and pentose (d-xylose and l-arabinose) substrates, as well as high tolerance to xylose at concentrations of up to 300 g/L. Optimal xylitol fermentation conditions were achieved at 32 °C, 140 rpm, pH 5.0, and initial cell concentration OD600 of 2.0, with YP (yeast extract 10 g/L, peptone 20 g/L) as the optimal nitrogen source. Xylitol yield increased from 0.61 g/g to 0.91 g/g with an increase in initial substrate concentration from 20 g/L to 180 g/L. Additionally, 20 g/L glycerol was found to be the optimal co-substrate for xylitol fermentation, resulting in an increase in xylitol yield from 0.82 g/g to 0.94 g/g at 140 rpm, enabling complete conversion of xylose to xylitol.

Uranium removal in groundwater by Priestia sp. isolated from uranium-contaminated mining soil

Priestia sp. WW1 was isolated from a uranium-contaminated mining soil and identified. The uranium removal characteristics and mechanism of Priestia sp. WW1 were investigated. The results showed that the removal efficiency of uranium decreased with the increase of initial uranium concentration. When the uranium initial concentration was 5 mg/L, the uranium removal efficiency achieved 92.1%. The increase of temperature could promote the uranium removal. Carbon source could affect the removal rate of uranium, which was the fastest when the methanol was used as carbon source. The solution pH had significant effect on the uranium removal efficiency, which reached the maximum under solution pH 5.0. The experimental results and FTIR as well as XPS demonstrated that Priestia sp. WW1 could remove uranium via both adsorption and reduction. The common chloride ions, sulfate ions, Mn(II) and Cu(II) enhanced the uranium removal, while Fe(III) depressed the uranium removal. The Priestia sp. WW1 could effectively remove the uranium in the actual mining groundwater, and the increase of initial biomass could improve the removal efficiency of uranium in the actual mining groundwater. This study provided a promising bacterium for uranium remediation in the groundwater.

The comparison of polymerization activity of typical cationic quaternary ammonium salt monomers

AbstractThe cationic water‐soluble polymers, which are widely used in many areas such as papermaking and separation process, are typically synthesized through polymerization of cationic monomers represented by quaternary ammonium salt. In this work, the polymerization reaction kinetics of three typical quaternary ammonium salt cationic monomers including acryloyl oxygen ethyl trimethyl ammonium chloride (DAC), methyl acryloyl oxygen ethyl trimethyl ammonium chloride (DMC), and methyl acrylamide propyl trimethyl ammonium chloride (MAPTAC) was examined by using the dilatometer method. The results showed that the polymerization rate of all three monomers increased with the increase of initiation temperature, monomer concentration, and initiator concentration. Under the same conditions, the polymerization activity of the three monomers followed the order: DAC > DMC > MAPTAC. The activation energies for the polymerization reaction under the specified conditions were EaDAC = 138.97 kJ/mol, EaDMC = 141.24 kJ/mol, and EaMAPTAC = 226.97 kJ/mol, respectively. The polymerization rate equations were RpDAC = k1[M]4.25[I]0.51, RpDMC = k2[M]3.77[I]0.50, and RpMAPTAC = k3[M]3.30[I]0.49. The polymerization activity of the monomers may be influenced by electronic effects and steric hindrance of the monomer structure. This work has provided a theoretical and experimental foundation for the actual work of structural design and preparation of cationic water‐soluble polymers.

The Catalytic Activity Of Manganosite MnO/Activated Carbon For Photo-Degradation Of Synthetic Dye

Photocatalytic degradation of organic dye such as methylene blue (MB) has been on focused various research interest due to environmental impact. In this study, the composite manganosite MnO/activated carbon was synthesized by a facile one-pot of solgel method through the reaction between potassium permanganate, glucose and commercial activated carbon. The XRD result revealed the presence of rock-salt manganosite MnO in the composite. The catalytic studies were performed under different solution pH, different catalyst concentration and various initial MB concentrations. The result indicated that the catalyst is very effective for the degradation of MB at the basic condition (pH 9 and p11). The degradation of MB in an acidic environment, however, is much less than that of basic condition. In addition, an increase in initial MB concentration caused a decrease in MB degradation due to the saturation of the active sites of the catalyst. The maximum degradation of MB was 98.86 % achieved at pH 11, the initial MB concentration of 50 ppm, and the catalyst concentration of 35 mg.

Novel biocomposite (Starch/metal–organic framework /Graphene oxide): Synthesis, characterization and visible light assisted dye degradation

Herein a new efficient biocomposites containing Starch metal–organic framework (MIL88A) and graphene oxide (Starch/MIL88A/GO) with different amounts of starch (0.05 0.1 and 0.2 g denoted as SMGO-0.5 SMGO-1 and SMGO-2) was synthesized characterized and used to degrade Acid Blue 92 (AB92). Decolorization efficiency was 7.4 % for Starch 19.4 % for GO 86 % for MIL88A and 90–98.5 % for Starch/MIL88A/GO composites (90 % for SMGO-0.5 96 % for SMGO-1 and 98.5 % for SMGO-2) using visible light. SMGO-2 composite showed the highest degradation ability. The effect of catalyst dosage and contaminant concentration on decolorization percentage was investigated. The efficiency of photocatalytic decolorization using 0 4 6 8 and 10 mg of Starch/MIL88A/GO are as follow: 10 55 89 93 and 98.5 % respectively. The results indicate that the decolorization by Starch/MIL88A/GO decreases as the initial pollutant concentration increases. Different decolorization kinetics (zero-order first-order and second-order) were studied. The reaction followed the zero-order kinetics. The zero-order decolorization rate constant for 0 4 6 8 and 10 mg of Starch/MIL88A/GO were 0.0134 0.1086 0.1182 0.1308 and 0.1727 respectively. The Starch/MIL88A/GO had high reusability (95 % after five cycles). The results indicated that the synthesized biocomposite (Starch/MIL88A/GO) could be used as an efficient photocatalyst to remove dye from the colored wastewater.

Use of oak acorns adsorbent and response surface methodology for removal of crystal violet from aqueous solution

ABSTRACTThis study investigates the potential use of oak acorn pericarp powder as an effective adsorbent for removing crystal violet from aqueous solutions under citric acid activation. Various analytical techniques, including FTIR, EDS, and SEM, were used to examine the characteristics of the adsorbent obtained. Throughout the experiments, parameters such as adsorbent quantity, solution pH, and initial dye concentration were meticulously taken into account. To optimise this removal process, a customised experimental approach based on response surface methodology (RSM) was adopted, involving the performance of 20 series of experiments to assess the influence of key variables, including adsorbent dose (A), pH (B), and initial dye concentration (C), as well as their interactions. Statistical analysis reveals the high significance of the elimination model, supported by an extremely low probability value (p < 0.0001). Notably, increasing adsorbent mass and solution pH leads to higher rates of crystal violet removal. Conversely, as the initial dye concentration increases, the removal rate decreases. Furthermore, the interaction between these variables does not appear to have a significant influence. Under optimal conditions, a remarkable elimination rate of 99.96% was achieved. This involved a solution with an initial pH of 10.82, an adsorbent dose of 28.5 mg, and an initial dye concentration of 17.8 mg/L. The kinetics of crystal violet adsorption onto the adsorbent were effectively described by a pseudo-second-order equation. Additionally, the optimal multilayer uptake capacity of OA@CA for CV dye was determined to be 135.9 mg.g−1, and the Freundlich model demonstrated a significantly better fit to the experimental results when compared to the Langmuir model.

Removal of fluoride from ground water by electrocoagulation method: investigation of process parameters, kinetic analysis, and operating cost

In the current study, aluminum electrodes have been employed in electrocoagulation (EC) to remove fluoride ions from groundwater. The effects of various operating process variables of EC, including pH, salt dosage, stirring speed, inter-electrode distance, and current density have been studied, as well as the operating cost and kinetics of the process. The most favorable values of the EC process parameters have been observed, which are effective for the removal of 97.6% fluoride, such as an initial value of pH 7.0, a current density value of 105.86 A/m2, an IED of 1 cm, a dose of salt of 0.33 g/L, a rotating speed of 700 RPM, and a time 40 min. The operating cost for the removal of fluoride (97.6% efficiency) from groundwater by EC was found to be 0.27 US$/m3. The effectiveness of the EC process in the removal of turbidity and TDS from different operating circumstances have also been investigated. First-order kinetics was observed in the kinetic study. The reaction rate constant k increases with CD increase, k decreases with IED increase, and k decreases with initial concentration increase. EDX analysis and FTIR spectra of the sludge confirm the availability of trace amounts of fluoride in the sludge produced. The EC process can effectively reduce the fluoride concentration from synthetic water as well as real groundwater up to below 1.5 mg/L as per WHO recommendations for drinking water.

Photocatalytic reduction of hexavalent chromium using Zn2SnO4–ZnO modified g-C3N4 composite

In this study, a novel hierarchical g-C3N4/Zn2SnO4–ZnO heterojunction system was reported as an efficient photocatalyst for the reduction of Cr(VI). The fabrication of the composite involved the synthesis of the complex metal oxide (Zn2SnO4–ZnO), followed by the in-situ integration into graphitic carbon nitride. The structure, morphology, and optical properties of the as-prepared tertiary composite were determined using various analytical techniques. The results indicated the improvement in surface area and the electronic structure of the semiconductor heterostructures. Photocatalytic measurement showed the efficiency of the ternary composite to cause a reduction of the band gap energy, delayed charge recombination process and enhancement of the visible light absorption. Reaction parameters including the solution pH, photocatalyst (g-C3N4/ZTO-ZnO) dosage, and the initial concentration of Cr(VI) on the degradation efficiency of the photocatalyst were evaluated. The solution pH was varied from 2 to 8, and pH 2 displayed the highest removal of Cr(VI) with 99.2 % removal efficiency for the g-C3N4/ZTO-ZnO, while the ZTO-ZnO exhibited 72 % efficiency. Finally, the kinetic study of the photocatalytic reaction showed an increase in the overall rate constant k with the increase in initial concentration of Cr(VI). The outstanding performance of the ternary composite compared to the bare complex metal oxide makes the innovative g-C3N4/Zn2SnO4–ZnO composite a promising material for the removal of Cr(VI) from aquatic environment.

Retention properties and mechanism of agricultural waste maize whisker on atmospheric mercury

Mercury (Hg) is a global pollutant transmitted mainly through the atmosphere, posing a serious threat to biological survival and human health. Porous materials, with high specific surface area, high porosity, and high adsorption, are particularly suitable for the purification of atmospheric Hg mixtures. However, plant porous materials are rarely directly used for atmospheric Hg purification. In this study, the properties and mechanism of maize whisker in removing atmospheric Hg were analyzed. The results show that the Hg content in the whiskers increases significantly as the initial Hg concentration increases, and 79.38% Hg can be removed by 0.2 g maize whiskers after 1 h exposure when the initial Hg concentration is 0.1 μg m−3, indicating that maize whiskers can accumulate atmospheric Hg rapidly and effectively. The hole diameter of the maize whisker is between 0.83 and 3.06 μm, which is suitable for the adsorption of small substances. Correlation analysis shows that maize whiskers have a significant correlation between atmospheric Hg retention and its specific surface area, pore size, medium pore ratio, and micropore ratio, suggesting that the maize whisker hole feature has a significant influence on its ability to retain atmospheric Hg. Compared with the energy profiles before and after Hg treatment, the peak of Mg decreased after Hg adsorption. Fourier infrared spectrometer analysis suggests that functional groups such as -OH, -COOH, and -O- are involved in the adsorption process. The change in pH value shows an obvious effect on the overall change in zeta potential in the adsorption process. Therefore, a variety of mechanisms, including physical adsorption, electrostatic adsorption, complexation, chelation, and ion exchange, are involved in Hg retention with the maize whisker. This study reveals the important potential value of agricultural waste maize whiskers in the purification of atmospheric heavy metal Hg.Graphical

Raw sawdust utilization for the removal of acid red57 and basic fuchsin dyes from aqueous solution: equilibrium, kinetics, and thermodynamic investigation

The aim of work is the use of a cheap adsorbent; sawdust (SD), for the adsorption of anionic dye, acid red57 (AR57), and cationic dye, basic fuchsin (BF). The adsorption of AR57 and BF on SD increased by increasing contact time and adsorbent dosage, while decreased with the increase of temperature and initial dye concentration. The increase in pH decreased the adsorption of AR57 and increased the adsorption of BF. The effective pH, adsorbent dose, and contact time on the AR57 removal efficiency were found to be 3, 0.1 g and 50 min, respectively. While for BF it was found to be 6, 0.2 g and 50 min, respectively. Fitting equilibrium data to Langmuir, Freundlich and Temkin isotherms showed that Freundlich model is the most suitable to describe the acid red57 and basic fuchsin. The kinetic studies indicate that the adsorption of AR57 and BF follows a pseudo-second-order model. The adsorption of both AR57 and BF is spontaneous (ΔG = −3.97, −3.27 kJ/mol) and exothermic (ΔH = −22.9, −8.3 kJ/mol) with negative values of ΔG and ΔH. The negative values of ΔS of both AR57 and BF (ΔS = −64.6, −16.7 J/mol. K) showed that the randomness decreases through the adsorption process.

Adsorption of Acid Yellow 23 Dye on Organobentonite/Alginate Hydrogel Beads in a Fixed-Bed Column

This research evaluates the use of organoclay/alginate hydrogels in removing Acid Yellow 23 in a fixed-bed column and contributes to the application of these composites in the context of the adsorption of anionic dyes that are present in wastewater. An organobentonite (OBent) was synthesized and encapsulated in an alginate matrix, using Ca2+ ions as a crosslinking agent. Experiments in fixed-bed columns showed that breakthrough and exhaustion times were longer with increasing bed height, which decreased with increases in flow rate and initial dye concentration. The Thomas, Yoon–Nelson, and Adams–Bohart models were well fitted to the experimental data for the breakthrough curves with high Adj. R2 correlation coefficients and low values of χ2. The theoretical adsorption capacity of the organobentonite/alginate hydrogel calculated from the Thomas model was 0.50 ± 0.01 mg/g (equivalent to 30.97 mg/g OBent), and this was obtained by using a 15 cm (10.10 g) bed height, 1 mL/min flow rate, and a 45 mg/L input dye concentration. The bed was regenerated with a 0.5 M NaOH solution, and the reuse of the saturated column bed was studied for two adsorption–desorption cycles. The results obtained in this study suggest the potential use of an organoclay/alginate hydrogel for the adsorption of pollutants in continuous systems.

Effect of gas components on the degradation mechanism of o-dichlorobenzene by non-thermal plasma technology with single dielectric barrier discharge

In this paper, the degradation of o-DCB under different gas-phase parameter conditions was investigated using the SDBD-NTP system. The results showed that the increase in initial and oxygen concentrations had opposite effects on the degradation of o-DCB. Among them, the increase of oxygen concentration promoted the degradation of o-DCB. Relative humidity promoted and then inhibited the degradation of o-DCB. The highest degradation efficiency of o-DCB was achieved at RH = 15%, reaching 91% at 29W. In the study of by-products, it was found that O3 and NOx were the main inorganic by-products, and that different oxygen levels and relative humidity conditions had a large effect on the production of O3 and NOx. In all of them, the concentration of O3 decreased with the increase of input power. NOx increased with increasing oxygen concentration, but the increase in relative humidity inhibited the production of NO and N2O and promoted the conversion of NO2. A study of organic by-products revealed this. In the absence of oxygen, a higher number of benzene products appeared. Whereas, with the addition of oxygen, only in the by-products under conditions where no relative humidity was introduced, benzene ring products were predominantly present in the by-products. However, when RH was added, n-hexane was found to be present in the by-products. This may be because the introduction of OH• favors the destruction of the benzene ring. Finally, the possible reaction pathways and reaction mechanisms of o-DCB under different gas-phase parameters are given. It provides a reference for future related scientific research as well as scientific problems in practical applications.