Pseudo-first Order Kinetic Model Research Articles

Acetylated corn and potato starches as an alternative to the toxic inorganic coagulants/flocculants for wastewater treatment

Inorganic coagulants/flocculants have been key in water treatments. However, last years, it has been reported the potential contamination that these give to the environment and serious risks to human health. For that reason, new eco-friendly alternatives have been the subject of exploration and research. This work focused on developing and elaborating a natural flocculant based on corn and potato starches, and its application in industrial wastewater treatments. Starches were isolated from corn and potato, and modified by acetylation method with the aim of improve its solubility. The morphological characterization using SEM identified the effects of acetylation process, the surface of acetylated corn and potato starches presented small erosions. The vibrational characterization via FTIR elucidated the physicochemical changes owing to acetylation. It found the replace of hydroxyl groups of α-glucose by the acetyl ones of amide I. A loss of the crystalline quality of corn starch were identified through structural characterization utilizing DRX. The partial replacement of hydroxyl by acetyl groups due to acetylation induced structural modifications corroborated employing the area under curve of the diffraction patterns. In the case of potato starch, its characteristic hexagonal crystalline structure was favored by the acetylation process, as it exhibited a more defined diffraction pattern. The thermal analysis by means of TGA found three thermal events for the acetylated potato starch and four for the acetylated corn starch. The fourth thermal event in the acetylated potato starch was associated with the ester presence of the added group. The thermal degradation occurred at lower temperatures as mass loss curves showed that acetylation weakened the polymer chains. The pH of zero point charge was 6.52 for the acetylated corn starch and 5.55 for the acetylated potato one, indicating that anionic contaminants be retained at a pH below 6.52 and 5.55 for each case, and the removal of cationic contaminants will favor at pH above these values. The efficiency determination of the modified starch-based flocculant was performed utilizing a jar test at different concentrations to find the optimal concentration of the coagulant/flocculant. Turbidity, color, pH, and electrical conductivity measurements were made before and after the water treatment. These results indicated that both corn and potato starches showed good performance as coagulants/flocculant. The kinetics for adsorption was study using the pseudo-first and pseudo-second order kinetic models, the intra-particle diffusion model, and the Elovich kinetic one. These analyzes identified that the absorption process is governed by chemisorption mechanisms since the pseudo-second order kinetic model was the most accurate for describing the absorption kinetic of both acetylated corn and potato starches according to the R2, SSE, MSE, and RMSE.

Raw Eggshell as an Adsorbent for Copper Ions Biosorption—Equilibrium, Kinetic, Thermodynamic and Process Optimization Studies

The study on the biosorption of copper ions using raw eggshells as an adsorbent is presented in this paper. The influence of different process parameters, such as: initial pH value of the solution, initial Cu2+ ions concentration, initial mass of the adsorbent, and stirring rate, on the biosorption capacity was evaluated. The SEM-EDS analysis was performed before and after the biosorption process. SEM micrographs indicate a change in the morphology of the sample after the biosorption process. The obtained EDS spectra indicated that K, Ca, and Mg were possibly exchanged with Cu2+ ions during the biosorption process. The equilibrium analysis showed that the Langmuir isotherm model best describes the experimental data. Four kinetic models were used to analyze the experimental data, and the results revealed that the pseudo-first order kinetic model is the best fit for the analyzed data. Calculated thermodynamic data indicated that the biosorption process is spontaneous, and that copper ions are possibly bound to the surface of the eggshells by chemisorption. The biosorption process was optimized using Response Surface Methodology (RSM) based on the Box-Behnken Design (BBD), with the selected factors: adsorbent mass, initial metal ion concentration, and contact time.

Novel dye removing agent based on CTS-g-P(AA-co-NIPAM)/GO composite

A novel composite Chitosan graft poly (acrylic acid-co-N-isopropylacrylamide)/graphite oxide (CTS-g-P(AA-co-NIPAM/GO) is synthesized and used to remove methylene blue (MB) and fuchsin basic (FB) from aqueous solutions by adsorption. Small amount of GO brings about great improvement of the thermostability together with the adsorption amount. Adsorption capacities of MB and FB increase from 842.1 and 633.7 mg/g, respectively, to 1496.3 and 1000.8 mg/g, respectively, with 0.02 g intercalation amount of GO. The interactions between GO and main body of CTS-g-P(AA-co-NIPAM) graft copolymer are hydrogen and amide bonds, whereas that between dye molecules and CTS-g-P(AA-co-NIPAM)/GO composite is hydrogen bond as well as electrostatic interaction. Effect of various conditions on the adsorption capacities is discussed. Adsorption isotherms and thermodynamics are studied. The adsorption of both MB and FB are spontaneous and satisfy the Redlich-Peterson equation. Kinetic study shows that the adsorption of both dyes is in accordance with the Pseudo first-order kinetic model.

Comparison of the performance of Ag-deposited ZnO and TiO2 nanoparticles in levofloxacin degradation under UV/visible radiation

This study has shown that the Ag-deposited ZnO and TiO2 nanoparticles can be ideally used to degrade and mineralize levofloxacin under UV radiation and with lower efficiency under visible light. The presence of Ag nanoparticles on the surface of photocatalysts contributes to the activation of the surface even under visible light; moreover, they effectively prevent the recombination of photogenerated electrons and holes by the metal oxides, resulting in higher performance of these modified photocatalysts. The best nominal Ag loading and catalyst dosage were 5 wt% and 1 g/L, respectively, and resulted in 99 and 91% levofloxacin removal for Ag/ZnO and Ag/TiO2 under UV irradiation. These values decreased to 56 and 49% under visible light due to the lower photon energy that can only activate Ag. The total organic carbon removal was also measured under UV irradiation, resulting in 97% and 84%, respectively. The kinetics of photocatalytic degradation followed the pseudo-first order kinetic model, and under all conditions, the kinetic rate constant of the ZnO-based photocatalysts was higher than that of the TiO2-based samples. Considering the contribution of dark adsorption in the first 30 min of the process, the pure photocatalytic performance of Ag-deposited ZnO was much more pronounced than Ag/TiO2. This contribution was 36 and 24% for Ag/ZnO and Ag/TiO2 (with 10 wt% Ag), respectively, when the degradation occurred under visible light. The cyclic performance of the photocatalysts showed reasonable results and no significant loss of performance was observed.

Adsorption characteristics of dopamine by activated carbon: Experimental and theoretical approach

In this work, we investigate the adsorption mechanism of dopamine (DP) drug using an activated carbon (AC) type through experimental and theoretical data. Experiment series were carried out at different initial values of solution pH, temperature, reaction time and initial drug concentration. The effect of protonation and deprotonation of DP molecule was also investigated. The equilibrium isotherm data were evaluated using the Dubinin-Radushkevich, Langmuir, Temkin and Freundlich models. Elovich, pseudo-first and pseudo-second order kinetic models were used to analyze kinetic data. Here we also used molecular dynamic (MD) simulation and DFT-based computational methods to reach information about the electronic properties of DP drug and its adsorption mechanism that have not been experimentally observed. Experimental results show that the Elovich kinetic model and Langmuir model best describe the adsorption phenomenon. In parallel, the experimental analysis revealed that the adsorption process is spontaneous and endothermic. Dopamine adsorption on AC occurs quickly and is pH and temperature-dependent. Frontier molecular orbital (FMO) energies for neutral, deprotonated and protonated forms of DP were determined and thoroughly explained. The basic medium significantly impacts DP drug adsorption behavior, which has the greatest adsorption energy when the pH is less than 12. It was found that DP adsorption occurs in a bidentate geometry by forming strong bonds between molecular oxygens and carbon atoms on the AC surface. Based on theoretical calculations interaction mechanisms of DP on the AC (001) surface were proposed.

Degradation of Agro-Industrial Wastewater Model Compound by UV-A-Fenton Process: Batch vs. Continuous Mode.

The degradation of a model agro-industrial wastewater phenolic compound (caffeic acid, CA) by a UV-A-Fenton system was investigated in this work. Experiments were carried out in order to compare batch and continuous mode. Initially, batch experiments showed that UV-A-Fenton at pH 3.0 (pH of CA solution) achieved a higher generation of HO•, leading to high CA degradation (>99.5%). The influence of different operational conditions, such as H2O2 and Fe2+ concentrations, were evaluated. The results fit a pseudo first-order (PFO) kinetic model, and a high kinetic rate of CA removal was observed, with a [CA] = 5.5 × 10-4 mol/L, [H2O2] = 2.2 × 10-3 mol/L and [Fe2+] = 1.1 × 10-4 mol/L (kCA = 0.694 min-1), with an electric energy per order (EEO) of 7.23 kWh m-3 order-1. Under the same operational conditions, experiments in continuous mode were performed under different flow rates. The results showed that CA achieved a steady state with higher space-times (θ = 0.04) in comparison to dissolved organic carbon (DOC) removal (θ = 0-0.020). The results showed that by increasing the flow rate (F) from 1 to 4 mL min-1, the CA and DOC removal rate increased significantly (kCA = 0.468 min-1; kDOC = 0.00896 min-1). It is concluded that continuous modes are advantageous systems that can be adapted to wastewater treatment plants for the treatment of real agro-industrial wastewaters.

Kinetics and Thermodynamics of Adsorption for Aromatic Hydrocarbon Model Systems via a Coagulation Process with a Ferric Sulfate-Lime Softening System.

The adsorption mechanisms for model hydrocarbons, 4-nitrophenol (PNP), and naphthalene were studied in a coagulation-based process using a ferric sulfate-lime softening system. Kinetic and thermodynamic adsorption parameters for this system were obtained under variable ionic strength and temperature. An in situ method was used to investigate kinetic adsorption profiles for PNP and naphthalene, where a pseudo-first order kinetic model adequately described the process. Thermodynamic parameters for the coagulation of PNP and naphthalene reveal an endothermic and spontaneous process. River water was compared against lab water samples at optimized conditions, where the results reveal that ions in the river water decrease the removal efficiency (RE; %) for PNP (RE = 28 to 20.3%) and naphthalene (RE = 89.0 to 80.2%). An aluminum sulfate (alum) coagulant was compared against the ferric system. The removal of PNP with alum decreased from RE = 20.5% in lab water and to RE = 16.8% in river water. Naphthalene removal decreased from RE = 89.0% with ferric sulfate to RE = 83.2% with alum in lab water and from RE = 80.2% for the ferric system to RE = 75.1% for alum in river water. Optical microscopy and dynamic light scattering of isolated flocs corroborated the role of ions in river water, according to variable RE and floc size distribution.

Separation, purification, and crystallization of 1,5-pentanediamine hydrochloride from fermentation broth by cation resin.

1,5-Pentanediamine hydrochloride (PDAH) was an important raw material for the preparation of bio-based pentamethylene diisocyanate (PDI). PDI has shown excellent properties in the application of adhesives and thermosetting polyurethane. In this study, PDAH was recovered from 1,5-pentanediamine (PDA) fermentation broth using a cation exchange resin and purified by crystallization. D152 was selected as the most suitable resin for purifying PDAH. The effects of solution pH, initial temperature, concentration of PDA, and adsorption time were studied by the static adsorption method. The equilibrium adsorption data were well fitted to Langmiur, Freundlich, and Temkin-Pyzhev adsorption isotherms. The adsorption free energy, enthalpy, and entropy were calculated. The experimental data were well described by the pseudo first-order kinetics model. The dynamic experiment in the fixed bed column showed that under optimal conditions, the adsorption capacity reached 96.45mgg-1, and the recovery proportion of the effective section reached 80.16%. In addition, the crystallization of the PDAH solution obtained by elution proved that the crystal product quality of resin eluting solution was highest. Thus, our research will contribute to the industrial scale-up of the separation of PDAH.

Photocatalysis of carbamazepine via activating bisulfite by ultraviolet: Performance, transformation mechanism, and residual toxicity assessment of intermediates products

Carbamazepine (CBZ) as an extensively distributed emerging pollutant has menaced ecological security. The degradation performance of CBZ by UV driven bisulfite process was investigated in this work. The kinetics results indicated that CBZ was high-efficiently degraded by UV/bisulfite following a pseudo first-order kinetic model (Kobs = 0.0925 min−1). SO4•− and •OH were verified as the reactive oxidants by EPR test and the radicals scavenging experiment using MeOH and TBA. SO4•− played a dominant role for CBZ degradation. The Density functional theory (DFT) and LC-qTOF-MS/MS clarified that hydroxylation, ketonation, ring opening reaction, and ring contraction were main transformation patterns of CBZ. As to influence factors, CBZ degradation was significantly hindered in presence of CO32−, HPO42− and NOM. Toxicological analysis derived from metabonomics suggested that the remarkable alteration of metabolic profile was triggered by exposure to intermediates mixture. CBZ intermediates interfered in several key metabolic pathways, including pentose phosphate, amino acids, lysine degradation, glycerophospholipid, glutathione, nucleotides and carbohydrate, which was alleviated after UV/bisulfite treatment. This work provided a meaningful support to potential risk of CBZ intermediates products, which shed light on the future application in eliminating drugs using UV /bisulfite.

Lagenaria siceraria Stem Nano Carbon Adsorption Kinetics and Thermodynamics of Malachite Green Dye

Among the most significant industrial pollutants are dyes, notably in the textile industry. Many techniques have been put forth to remove colour from wastewater, but adsorption is the most widely accepted since it can be applied on a broad scale. The Malachite Green dye has been removed from aqueous settings using this work’s application of Modified Activated Lagenaria siceraria Stem Nano Carbon (ALSNC). The effects of pH, contact time, starting concentration, and adsorbent quantity were taken into account. Pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models were among those utilised to examine the mechanism of the adsorption process. Additionally, equilibrium data was fitted to the Radlich-Peterson isotherm model as well as the Langmuir, Freundlich, and Dubinin-Radushkevich, isotherm models. As a result of raising initial dye concentration, pH, and contact duration, the Malachite Green’s ability to bind to surfaces was improved, according to the results. pH 9 was the ideal level. Malachite Green dye adsorption had a qmax of 15.87 mg/g according to the Langmuir model. The Freundlich isotherm model and the pseudo-second order kinetic model obtained the best fitness when taking into account the values of R2 (0.999) and 2. This work has shown that ALSNC can be used as a cost-effective and efficient adsorbent for the removal of Malachite Green from aquatic environments

The Removal of Dye from Synthetic Wastewater using Hybrid Modified Sugarcane Bagasse-Banana Stem

The potential application of hybrid adsorbents for sugarcane bagasse and banana stem has been explored through the use of a batch adsorption experiment. To ascertain the impact of various dosages and contact times, several experiments were conducted. The Langmuir and Freundlich isotherm models were used to conduct the adsorption analysis. Apart from that, the behaviour and mechanism were analysed utilising the Pseudo-first order and Pseudo-second order kinetic models. The findings reveal that in 100 mL of synthetic dye sample, at an optimal dosage of sugarcane bagasse and banana stem, and at an optimal contact time of 65 minutes, more than 80% of the colour was eliminated. Isotherm models showed that the study was best fitted to Langmuir with a coefficient correlation R2 of 0.9048. In addition, the adsorption kinetics of colour showed that pseudo-second order well-fitted with the coefficient correlation 0.9639, which is bigger than pseudo-first order, 0.4827. Due to the low cost of the media utilised in the study, the hybrid adsorbents of sugarcane bagasse and banana stem have a good potential for colour removal in textile wastewater treatment. As a result, it provides an alternate method of addressing issues associated with an excess of colour in dye wastewater treatment plants.

Polyamide microplastics as better environmental vectors of Cr(VI) in comparison to polyethylene and polypropylene microplastics

The adsorption, desorption, and their influence factors of Cr(VI) by microplastics (MPs) in the solution was investigated in this study. The results demonstrated that UV aging promoted adsorption, while the increase of salinity and natural organic matter (NOM) inhibited adsorption. The particle size affected the total Cr(VI) active adsorption sites on MPs, while the pH changed the electrostatic force. The Cr(VI) adsorption by MPs conformed to the pseudo-first and pseudo-second order kinetic models, and was monolayer and inhomogeneous. SEM-EDS, XPS and ATR-FTIR analyses demonstrated that the physical adsorption dominated the adsorption process. Especially, the highest adsorption capacity of Cr(VI) by polyamide (PA) MPs was attributed to their hydrophilic amide groups. However, Cr(VI) was only released from PA MPs, of which desorption rate followed the sequence of seawater (79.5 %) > fresh water (66.6 %) > deionized water (34.8 %). Thus, PA MPs might be non-negligible environmental vectors for the transport of Cr(VI).

Predicting the bioavailability of nitro polycyclic aromatic hydrocarbons in sediments: ZIF-8/h-BN solid-phase microextraction versus Tenax extraction

The occurrence of nitrated polycyclic aromatic hydrocarbons (NPAHs) in sediments has been widely reported, but research on NPAH bioavailability is lacking. In this study, a self-made zeolite imidazolate framework-8/hexagonal boron nitride (ZIF-8/h-BN) solid-phase microextraction (SPME) fiber and commercial Tenax are compared as efficient tools to predict the bioavailability of NPAHs in sediments with bioassays using Cipangopaludina chinensis. During the process of SPME, the NPAH concentrations on the ZIF-8/h-BN fibers reached extraction equilibrium after 72 h. The fiber extraction of NPAHs in sediments was well-fitted by the pseudo first-order kinetic model with a rate constant of 2 × 10−2 h−1 (R2 > 0.98). The extraction rates ranking of NPAHs in sediments was 2-nitrobiphenyl>1-nitropyrene>5-nitroacenaphthene>2-nitrofluorene. Compared with SPME, NPAH concentrations reached equilibrium after 168 h for the Tenax extraction. The orders of magnitude of fast, slow, and very slow desorption rate constants were 10−1, 10−2, and 10−4, respectively. At extraction equilibrium (168 h), the SPME was close to the bioavailability of the NPAHs in sediments to Cipangopaludina chinensis with a slope statistically approximated to one. In addition, the linear regression for SPME (R2 = 0.7285) was slightly higher than that of the Tenax extraction (R2 = 0.7168) over a short time (6 h). This could be because the coating material of ZIF-8/h-BN can rapidly adsorb freely dissolved NPAHs, and the SPME fibers can accurately predict the bioaccumulated concentrations of NPAHs in exposed organisms by measuring the concentration of NPAHs in the pore water of sediment. This study provides a time-saving and easy procedure to predict the bioavailability of NPAHs in sediments.

Complexes of terpyridine scaffold as efficient photocatalysts for the degradation of methylene blue pollutant in wastewater effluents

In the present protocol, a series of varyingly substituted terpyridine-based ligands have been designed and synthesized. The synthesized ligands were coordinated with different transition metal cations. Their complexation with Fe(II), Co(II) and Zn(II) led to interesting coordination compounds which for the first time, were evaluated for their photocatalytic potential against the degradation of methylene blue. Almost all the tested complexes 1–9 exhibited fascinating photocatalytic properties. However, noteworthy, photocatalytic results revealed that zinc complexes 1 ([Zn (4′-(p-tolyl)-2,2′:6′,2″-terpyridine)(SO4)2−]), 4 ([Zn (N,N-Dimethyl-4-(2,2′:6′,2″-terpyridin-4′-yl)aniline)(SO4)2−]) & 7 ([Zn (N,N-Diphenyl-4-(2,2′:6′,2″-terpyridin-4′-yl)aniline)(SO4)2−]) have high potential against the degradation of methylene blue followed by iron complexes 3 ([Fe(4′-(p-tolyl)-2,2′:6′,2″-terpyridin)2](PF6)2), 6 ([Fe(4′-(N,N-Dimethyl-4-(2,2′:6′,2″-terpyridin-4′-yl)aniline)2]2PF6) &9 ([Fe(N,N-Diphenyl-4-(2,2′:6′,2″-terpyridin-4′-yl)aniline)2]2PF6) and then cobalt complexes 2 (Co(4′-(p-tolyl)-2,2′:6′,2″-terpyridin)2](PF6)2), 5 ([Co(4′-(N,N-Dimethyl-4-(2,2′:6′,2″-terpyridin-4′-yl)aniline)2]2PF6) &8 ([Co(N,N-Diphenyl-4-(2,2′:6′,2″-terpyridin-4′-yl)aniline)2]2PF6). Among all the complexes, maximum degradation efficiencies were observed for complex 1 (67.31 %) and complex 7 (65.91 %). The optimized photocatalytic conditions were found to be 10 mg/L of initial concentration of dye solution, 20 mg of catalyst dose, pH = 4 and irradiation time of 40 min. At optimized conditions complex 7 was found to be more efficient photocatalyst with rate constant value of 0.011 min−1 as compared to the rate constant value of 0.009 min−1 for complex 1. Both complexes followed the pseudo-first order kinetics model. The reusability test indicated only 8.62 % and 7.01 % loss of photocatalytic activity for complex 1 and complex 7, respectively, up to four cycles of photodegradation reflecting that these catalysts can be used again and again. This study suggested the remarkable potential of terpyridine metal complexes for the environmental remediation to remove harmful pollutants from aqueous bodies.

TiO2/Bi2O3/PANI nanocomposite materials for enhanced photocatalytic decontamination of organic pollutants

• TiO 2 /Bi 2 O 3 /PANI nanocomposites were synthesized. • Materials characterized for structural, morphological and optical characteristics. • Nanocomposites employed for RhB and Triclopyr photocatalytic degradation. • Close contact between TiO 2 , Bi 2 O 3 and PANI promotes interfacial charge transfer. • holes are the prominent ROS for the degradation of RhB; holes and O 2 ∙ - for TC. In this present work, TiO 2 /Bi 2 O 3 /PANI nanocomposites were synthesized and employed as photocatalyst for the degradation of organic pollutants i.e. Rhodamine B dye and Triclopyr pesticides. TiO 2 /Bi 2 O 3 /PANI nanocomposites were characterized with the help of various advanced instrumentation techniques including X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (UV-vis DRS), photoluminescence (PL), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analysis. The absorption in the visible wavelength region (λ > 400 nm) increased with increasing PANI amount accompanied by π → π ∗ transition. The close contact between TiO 2 , Bi 2 O 3 and PANI promotes the interfacial charge transfer and significantly improved photocatalytic performance under the irradiation of visible LEDs. Among the prepared nanocomposites, the sample containing 5 wt. % PANI of TiO 2 /Bi 2 O 3 (TB(15)) was found to be most efficient photocatalyst and stable even after four cyclic runs for the degradation of organic pollutants. TB(15)/PANI(5) exhibited the lowest PL intensity, indicating the minimum reunion in the photoproduced electron-hole pairs, which was favorable to improve the efficiency of the photocatalyst for the removal of organic pollutants. The photodegradation rate of RhB and TC using TB(15)/PANI(5) photocatalyst reached to 99.6 % in 50 minutes and 76.1 % in 120 minutes under the visible LEDs irradiation respectively. Kinetics analysis of photocatalytic reaction obeys the pseudo first-order kinetic model with respect to concentration of organic pollutants with a regression coefficient value in the range of 0.941-0.999. The trapping experiments confirmed that holes are prominent species for the degradation of RhB, and holes and superoxide anion radical for photocatalytic degradation of TC. Finally, the mechanism of photocatalytic degradation using TiO 2 /Bi 2 O 3 /PANI nanocomposite was also proposed.

Comparison of membrane fouling induced by protein, polysaccharide and humic acid under sodium and calcium ionic conditions

To further compare the effect of sodium and calcium on the membrane fouling mechanism of typical organic matters, the adsorption behavior of sodium alginate, humic acid and bovine serum albumin on PVDF membranes were explored by quartz crystal microbalance and dissipation (QCM-D), while the adhesion force between foulants and between the foulants and membrane were examined by using atomic force microscopy (AFM) detection with foulant-coated probes. Results demonstrated that the adhesion force between organic and membrane had significant impact on the adsorption rate at the initial fouling stage, whereas the interaction force among the organic was connected with the degree of irreversible fouling and the structure of the fouling layer. Ca2+ made organic fouling more severe and irreversible due to the complexation effect under the same ionic strength conditions, which is consistent with the XDLVO theory. Compared to the other two organics, BSA demonstrated deposition more in mass, higher in adsorption rate and irreversibility under both Ca2+ and Na+ conditions, which attributed to stronger interaction forces among BSA molecules and the thus formed denser fouling layer. During the adsorption process the pseudo-second-order agreed well with fouling behavior of SA and BSA, while HA conformed to the pseudo-first order kinetic model.

Nonthermal plasma-irradiated polyvalent ferromanganese binary hydro(oxide) for the removal of uranyl ions from wastewater

Nonthermal plasma (NTP) irradiation was employed to adjust the morphological structures and valence distribution of ferromanganese (Fe–Mn)-based binary hydro (oxide) to enhance the heterogeneous adsorption of uranyl ions. The output voltage and the liquid-plate distance played a more vital role among the NTP factors in the irradiation system in influencing the polyvalent Fe–Mn binary hydro (oxide) (poly-Fe-Mn). The formation of plates, flakes, and nanoscale nodules was specifically observed, which caused more pores and fractures in the poly-Fe-Mn binary hydro (oxide). The poly-Fe-Mn performed explicitly better in the adsorption of uranium ions in comparison with the counterpart of the Fe–Mn, which was appropriately fitted by the pseudofirst-order kinetic and Elovich models. Maximum equilibrium adsorption capacities of 663.92 and 923.45 mg/g were obtained for the Fe–Mn and poly-Fe-Mn binary hydro (oxides) toward U ions in the orthogonal design, respectively. The maximum monolayer adsorption capacity achieved by the fitting of the Langmuir model was 1091.10 mg/g. Both physisorption and chemisorption contributed to the heterogeneous process of the poly-Fe-Mn toward uranium ions. The employment of NTP irradiation changed the monolayer adsorption of the traditional Fe–Mn materials and diversified the reaction mechanisms between the interface of the Fe–Mn materials and uranium ions. The elements, including O, N, and U exhibited higher compatibility and overlapped in the samples. The highly effective capture of uranium ions from the solution by the poly-Fe-Mn binary hydro (oxide) was mainly related to the chemical deposition of O and N radicals.

On the applicability of triazine-based covalent organic polymer as adsorbent for dye removal from aqueous solution

Triazine-based covalent organic polymer, TCOP, is synthesized via the reaction between cyanuric chloride and piperazine in 1,4-dioxane, and is characterized with FT-IR, EDX, elemental mapping, XRD, SEM, TEM and N2 adsorption/desorption techniques. The capability of TCOP in the removal of different types of dye pollutants is studied and it was found that the removal efficiency is more than 70% for all of them. The kinetics and equilibrium adsorption of Rhodamine B (RhB) was studied at different conditions. Most of the adsorption takes place in less than 20 min and the maximum adsorption capacity is 153 mg/g. The adsorption isotherm can be well described by the modified Langmuir-Freundlich equation and the adsorption kinetics follows the fractal-like pseudo-first order kinetics model. Both of the fitted models reveal the heterogeneity of adsorbent. The adsorption thermodynamics parameters were calculated and interpreted. Finally, it was shown that the prepared TCOP can be used for the removal of dye mixture from aqueous solution.

Synthesis of novel carbon-supported iron oxide sorbents for adsorption of dye from aqueous solutions: equilibrium and flow-through studies

Textile effluents contain dyes that negatively affect water bodies and inhibit photosynthesis by reducing sunlight penetration. This study investigated the adsorption capacity of an iron oxide sorbent immobilised on naturally derived carbon foam for the removal of organic methylene blue dye from water. In this study, the carbon precursor and iron oxide precursor were mixed and carbonised in a single vessel. Baking and carbonization of the natural grain combination produce a porous structure that can act as an effective support for the iron oxide particles. The carbon foam prepared had a self-assembled structure with flour as a basic element. Sorbents of 6 weight (wt)%, 15 wt% iron, and a 0 wt% iron control sample were prepared. Transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) techniques were used to examine the synthesised carbon foam physical properties and surface morphology. The adsorption capabilities were investigated in batch tests by determining the effects of an increase in iron content, sorbent dosage, contact time, and dye concentration. Breakthrough curves were obtained by varying the height of the sorbent bed and varying the flowrate of the dye solution. A higher bed height corresponds to a greater amount of adsorbent. The breakthrough and equilibrium adsorption capacities were found to increase with increasing bed height. When the flow rate is high, the dye solution leaves the column before equilibrium, resulting in shorter breakthrough and saturation times. Higher bed heights and lower flow rates resulted in optimal dye removal in the flow through the system. Breakthrough time increases with increasing iron content. The 15 wt% iron sample displayed superior adsorption capabilities than the 6 wt% sample, while the 0 wt% iron control sample displayed minimal adsorptive capabilities. The pseudo-first order kinetic model was the best fit model for this study (R2 > 0.96), and the adsorption equilibrium is best described by the Freundlich isotherm (R2 > 0.99). The results showed that an iron oxide sorbent immobilised on carbon foam made from natural sources is a good adsorbent for removing methylene dye.

Ficus-mediated green synthesis of manganese oxide nanoparticles for adsorptive removal of malachite green from surface water

The extract of ficus leaves was used to prepare manganese (IV) oxide nanoparticles (MnO2 NPs) for the first time. Several different analytical techniques were used to characterize the prepared MnO2 NPs. MnO2 has spherical crystals that are ~ 7 nm on average in size and have 149.68 m2/g of surface area and 0.91 cm3/g of total pore volume. Malachite green (MG) dye was then taken out of the water by adsorption using MnO2 NPs. Optimization of various adsorption parameters resulted in 188.68–277.78 mg/g maximum adsorption capacities at 298–328 K tested temperatures and 99.6% removal of 50 mg/L MG within 90 min using MnO2 dose of 0.01 g at pH 10 and 298 K. The results were tested using pseudo-first order, pseudo-second order, intraparticle diffusion, Elovich, and Liquid film kinetic models as well as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherm models. The most likely models to describe the adsorption process at 298 K are pseudo-second-order kinetics (R2 = 0.997) with a rate constant of 4 × 10−4 g/(mg.min) and Langmuir isotherm (R2 = 0.973). Additionally, the positive values of enthalpy change (3.91–67.81 kJ/mol) and the negative values of Gibb’s free energy (− 3.38 to − 19.7 kJ/mol) indicate that the process is endothermic, spontaneous, and thermodynamically feasible. MnO2 NPs sustained their adsorption efficiency at 90.4% after 5 sorption cycles. MnO2 appears to be more selective for MG in studies examining the adsorption of various cationic dyes. Lately, the biosynthesized MnO2 NPs can be utilized to remove MG from aqueous solutions effectively.