Adsorption and photocatalytic detoxification of diazinon using iron and nanotitania modified activated carbons

Performance evaluation of PdO/ CuO TiO2 photocatalytic membrane on ceramic support for removing pharmaceutical compounds from water

This study investigated photocatalytic degradation of pharmaceutical compound using CuO or PdO-TiO2 membrane. The synthesized membranes were characterized by some techniques including X-ray powder diffraction (XRD), dynamic light scattering (DLS), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FT-IR). The structural properties confirmed that the photocatalytic membranes were successfully prepared on ceramic supports. The PdO-TiO2 and CuO-TiO2 membranes were employed as photocatalytic membranes to degrade metronidazole (MNZ) and diphenhydramine (DPH) in aqueous solutions, respectively. Some parameters affecting the photocatalytic reaction such as pH, initial concentration, and light source were also investigated. The maximum degradation for both pharmaceutical compounds was obtained at basic pH (pH = 10), low initial concentration (C0 = 10 ppm) under UV irradiation. At high transmembrane pressure (ΔP = 3 bar), the flow rate across the membrane increased up 0.0078 and 0.0082 cc/s.cm2 for CuO-TiO2 and PdO-TiO2 photocatalytic membrane respectively while not affected on degradation efficiency (DE). At the same condition operation (C0 = 10 ppm, pH = 10, ΔP = 2 bar under UV irradiation), the MNZ and DPH degradation of the PdO-TiO2 membrane was 94 and 95% respectively that relatively higher than the CuO-TiO2 membrane. It is probably due to the lower energy band gap of PdO-TiO2 (2.5 eV) than CuO-TiO2 (2.7 eV). The membrane stability tests confirmed the high performance of the prepared membranes.

Fabrication of titania/calcium alginate nanocomposite matrix for efficient adsorption and photocatalytic degradation of malachite green

This work aims to examine the two techniques' efficiency for the elimination of malachite green (MG) by photocatalytic degradation and adsorption onto synthesized solid nanomaterials. Three solid samples were prepared as calcium alginate (AG), nanotitania (NT), and nanotitania/calcium alginate composite (TG). The morphological and physicochemical characteristics of the solid nanomaterials were investigated by XRD, TGA, DRS, FTIR, pHPZC, nitrogen adsorption/desorption isotherm, SEM, and TEM. The main experimental conditions were determined for sample dose, shaking time, pH, initial malachite green concentration, temperature, ionic strength, and UV lamp power. The resulting data proved that TG attained the higher adsorption capacity (252.52 mg/g) at 40 °C. The adsorption of MG was well fitted by Langmuir, Temkin, Dubinin-Radushkevich, pseudo-second order, intra-particle diffusion, and Elovich models onto all the prepared samples, confirming the endothermic, spontaneous, and favorable adsorption process. The maximum degradation percent (99.6 %) of MG was achieved by using 1.0 g/L as a catalyst dose, 10 mg/L of initial MG concentration, and 33 W for TG. The photodegradation of MG was well fitted by Eyring-Polanyi and Arrhenius models onto the surface of catalyst. The TG reusability resulted in a decrease in the degradation efficiency by 9.8 %, indicating its great capacity as the first nanotitania/calcium alginate nanocomposite used in removing MG from wastewater by two technologies in the same article.

Visible light-driven ZnO/Fe3O4 magnetic nanoparticles for detoxification of diazinon: the photocatalytic optimization process with RSM-BBD model

Today, diazinon is one of the most widely used organophosphorus pesticides, whose widespread use can cause many ecological and biological risks. In this research, a magnetic ZnO/Fe3O4 nanoparticle was used to investigate the photocatalytic degradation of diazinon. Sol-gel synthesis was used to create the nanoparticle, which was then characterized using XRD, FTIR, FESEM, VSM, and XPS techniques. The design of photocatalytic degradation experiments was done using the response surface method and the Box-Behnken design model. The investigated parameters include pH, nanoparticle concentration, diazinon concentration, and irradiation time. The characterization of the ZnO/Fe3O4 nanoparticle showed well-formed crystalline phases and a cubic spinel structure. Additionally, the shape of the nanoparticle is almost uniform and spherical. The FT-IR spectrum also confirmed the presence of all functional groups related to ZnO and Fe3O4 in the ZnO/Fe3O4 nanoparticles structure. The synthesized nanocomposite has superparamagnetic properties and a very small coercive field, making it easily recyclable, according to a VSM analysis. XPS results also showed the presence of Fe (Fe 2p1/2 and Fe 2p3/2), Zn (Zn 2p1/2 and Zn 2p3/2), oxygen (O1s), and weak carbon (C1s) peaks in the ZnO/Fe3O4 structure. The results of the photocatalytic optimization experiments showed that the highest efficiency of diazinon toxin degradation is 99.3% under the conditions of pH 7, diazinon initial concentration of 10 mg/L, nanoparticle concentration of 1 g/L, and a contact time of 90 min. This result is very close to the BBD model's predicted removal efficiency under optimal conditions (100%). As a result, the ZnO/Fe3O4 nanocomposite can produce active free radicals through UV radiation, and these radicals can successfully remove diazinon under actual conditions.

Static adsorption and photocatalytic degradation of amoxicillin using titanium dioxide/hydroxyapatite nanoparticles based on sea scallop shells

The objective of this study is to investigate the efficiency of two processes for the amoxicillin removal through static (batch) adsorption and photocatalytic degradation onto the prepared samples. Three solid materials as photocatalyst and/or adsorbent were synthesized viz. nanotitanium dioxide (NT) prepared by the sol-gel method, scallop shells-based nanohydroxyapatite (NP), and nanotitanium dioxide/nanohydroxyapatite composite (NTP). The physicochemical and morphological properties of the prepared samples were tested by TGA, XRD, DRS, ATR-FTIR, nitrogen adsorption/desorption isotherm, zeta potential, SEM, and TEM. The major operational conditions were optimized for catalyst or adsorbent mass, pH, shaking time, initial amoxicillin (AMX) concentration, power of UV lamp, and temperature. The results illuminated that NTP achieved the highest adsorption capacity (88.46 mg/g) at 20 ℃ and AMX adsorption onto all the solid materials was well applied by Langmuir, Temkin, pseudo-second order, and Elovich models. The maximum desorption percent (98%) was attained by acetone. The degradation percent of AMX reached 85.3 and 99.5% for NT and NTP, respectively, using 0.9 g/L of catalyst dosage through 90 min. AMX photodegradation onto the catalysts' surface was well fitted by Langmuir-Hinshelwood, Arrhenius, and Eyring-Polanyi models with endothermic, physical, and nonspontaneous nature of photocatalysis process. NTP acts as a promising adsorbent and photocatalyst for the antibiotics' removal in wastewater.

Optimization of aflatoxin B1 removal efficiency of DNA by resonance light scattering spectroscopy

In this paper, firstly, the resonance light scattering spectra of aflatoxin B₁ (AFB₁) and DNA were measured by resonance light scattering spectroscopy (RLS), and the DNA binding saturation value (DBSV) of AFB₁ was calculated from their spectral results. Then the interaction intensity between DNA and AFB₁ and the effects of some external factors on the interaction between DNA and AFB₁ were evaluated by corresponding DBSVs, so as to establish and optimize a way for removing AFB₁ by DNA. DBSV of AFB₁ was 2.04 at 30℃ and pH 7.40. However, after adding sodium ion, calcium ion, vitamin E, vitamin C and D-glucose, DBSV of AFB₁ was changed to 2.72, 3.17, 2.67, 1.68 and 1.33 respectively. Correspondingly, the removal efficiency of AFB₁ by DNA was changed from 90.05% to 93.25%, 95.48%, 93.08%, 82.36% and 78.90% respectively. These results indicated that the external factors had a significant impact on the interaction between DNA and AFB₁. Among them, some factors enhanced the interaction between DNA and AFB₁, while some factors weakened the interaction between DNA and AFB1. The change of these external factors led to the corresponding changes in DBSV and the removal efficiency of AFB₁. DBSV of AFB₁ could really be used as an index to evaluate the intensity of the interaction between DNA and AFB₁, and to optimize the removal efficiency of AFB₁ by DNA. The experimental data also showed that the adsorption of AFB₁ to DNA was consistent with the pseudo-second-order kinetic model and the Freundlich isothermal model, was an exothermic and spontaneous process. All these results will give good references for establishing and optimizing a way of AFB₁ removal via DNA intercalation.

Multi-criteria decision-making for prioritizing photocatalytic processes followed by TiO2-MIL-53(Fe) characterization and application for diazinon removal

Multi-criteria decision-making (MCDM) can introduce the best option based on evidence. We integrated the Analytic Hierarchy Process (AHP) and the Technique for Order of Preference by Similarity to the Ideal Solution (TOPSIS) to prioritize the alternatives for photocatalytic diazinon removal in a bench scale and characterized TiO2-MIL-53(Fe) for this purpose. Criteria and alternatives were listed based on systematic literature reviews and expert opinions. Then, AHP and TOPSIS questionnaires were developed and distributed to an expert panel for pairwise comparisons. We converted the linguistic variables into the corresponding fuzzy values and used R for mathematical calculations. Then, TiO2-MIL-53(Fe) was synthesized and characterized for diazinon removal under LED visible light. The AHP ranked criteria as availability > degradation efficiency > safety for the environment > material cost > energy consumption > mineralization efficiency > photocatalyst reusability > safety for personnel > equipment cost. Based on TOPSIS, the order of alternatives was TiO2-containing/Visible light > ZnO-containing/UV light > TiO2-containing/UV light > ZnO-containing/Visible light > WO3-containing/UV light. With a bandgap of 1.8 eV, TiO2-MIL-53(Fe) could remove 89.35% of diazinon at 10 mg/L diazinon concentration, 750 mg/L catalyst dose, pH 6.8, and 180-min reaction time. Hybrid AHP-TOPSIS identified the best option for photocatalytic diazinon removal from aqueous solutions. Thus, MCDM techniques can use systematic review results to overcome the uncertainty in designing experimental studies.

Synthesis of nanomagnetite/copper oxide/potassium carrageenan nanocomposite for the adsorption and Photo-Fenton degradation of Safranin-O: kinetic and thermodynamic studies

In the current study, a novel nanomaterial called nanomagnetite/copper oxide/potassium carrageenan nanocomposite (MKCO) was fabricated to include Fenton (nanomagnetite, NM) and Fenton-like reagent (copper oxide nanoparticles, NCO) in a matrix of potassium carrageenan biopolymer. The prepared solid materials were characterized by different physicochemical techniques, such as TGA, N2 adsorption/desorption, SEM, TEM, XRD, DRS, pHPZC, and FTIR. The prepared MKCO showed unique properties like higher specific surface area of 652.50 m2/g, pore radius of 1.19 nm, pHPZC equals 7.80, and the presence of different surface chemical functional groups. Under various application conditions, comparative experiments between Safranin-O dye (SO) adsorption and Photo-Fenton catalytic degradation were conducted. After 24 h, MKCO had a maximum adsorption capacity of 384.61 mg/g at 42 °C, while the Photo-Fenton oxidation process took only 10 min to totally decompose 93% of SO at 21 °C. Based on the higher values of correlation coefficients, Langmuir’s adsorption model is the best-fitted adsorption model for SO onto all the prepared solid materials. Studies on SO adsorption’s kinetics and thermodynamics show that it is physisorption and that it operates according to endothermic, spontaneous, and PFO model processes. While, PFO, endothermic, and non-spontaneous processes are satisfied by the catalytic decomposition of SO. After five application cycles, MKCO demonstrated good catalyst reusability with a 3.4% decrease in degrading efficiency. For lower contaminant concentrations and shorter application times, Photo-Fenton catalytic degradation of organic pollutants is more effective than adsorption.

Graphical abstract

Fenton and Photo-Fenton degradation of Safranin-O

Utilizing modified cellulose nanoparticles derived from a plant loofah sponge to improve the removal of diazinon insecticide from an aqueous medium

Organophosphate insecticides, such as diazinon, have been well investigated to pose health and environmental risks. In this study, ferric-modified nanocellulose composite (FCN) and nanocellulose particles (CN) based on a natural source as a loofah sponge were synthesized to verify their adsorption potential to eliminate diazinon (DZ) from contaminated water. The as-prepared adsorbents were characterized by performing TGA, XRD, FTIR spectroscopy, SEM, TEM, pHPZC, and BET analyses, in which FCN showed high thermal stability, surface area of 82.65 m2 g-1, surface with mesopores, good crystallinity (61.6%), and particle size of 86.0 nm. The results of adsorption tests demonstrated that the maximum Langmuir adsorption capacity (294.98 mg g-1) was exhibited by FCN at 38 °C, pH 7, 1.0 g L-1 of adsorbent dosage, and 20 h of contact shaking time. The effect of adding KCl solution with high ionic strength (1.0 mol L-1) reduced the DZ removal percent by 52.9%. The experimental adsorption data achieved the best fit with all the applied isotherm models with favorable, physical, and endothermic nature of adsorption consistent with thermodynamic data. Pentanol attained higher desorption efficiency (95%) and was used in five adsorption/desorption cycles in which FCN exhibited only an 8.8% decrease in the removal percent of DZ.

Explanation of difenoconazole removal by chitosan with Langmuir adsorption isotherm and kinetic modeling

In this study, the adsorption of toxic difenoconazole pesticide was investigated by using chitosan. In the first phase of the study, chitosan was extracted from deep-water pink shrimp (Parapenaeus longirostris) shells, by deacetylation of the chitin, which is separated and disposed of after meat extraction in processing facilities in Turkey. The deacetylation degree, molecular weight, viscosity, moisture, and crude-ash values of the extracted chitosan were determined. Chitosan, having a high deacetylation degree (90.21%), was used as the adsorbent. In the second phase of the study, the effects of pH, temperature, and pesticide concentration on the adsorption were investigated. The optimum pH level for pesticide adsorption was determined as 5. It was observed that the adsorption increases as the temperature increases. A rapid increase was observed within the first 5 min of the 60-minute adsorption process in difenoconazole concentrations of 5, 15, and 25 µg/L, and after 10 min, the adsorption rate was stable. The Langmuir isotherm parameters regarding the adsorption were determined as aL = 0.635, kL = 15.10, and the Qmax value was calculated as 23.77 mg/g. In the evaluation of overall study results, it was determined that the chitosan biopolymer is a suitable adsorbent for difenoconazole pesticide adsorption.

Enhanced Removal of Bordeaux B and Red G Dyes Used in Alpaca Wool Dying from Water Using Iron-Modified Activated Carbon

The aim of this research was to explore the removal of Red G and Bordeaux B dyes from water using a packed bed column with conventional carbon (C‐conv) and iron‐modified activated carbon (C–FeCl3). The bands increased in C–FeCl3, corresponding to groups already existing in C‐conv, such as C = C and C‐C, and the appearance of new groups, such as C‐O, C‐Cl, Fe‐Cl and Fe‐O. The total ash content (CT) was CT = (10.53 ± 0.12 and 8.98 ± 0.21)% for C‐conv and C–FeCl3, respectively. A molecular structure in the shape of a cross was noticed in Bordeaux B, which was less complex and smaller than the one in Red G. For fixed‐bed columns, the carbon fraction was (0.43 and 0.85) mm. The pH of the adsorbents was 8.55 for C‐conv and 4.14 for C–FeCl3. Breakthrough curves were obtained and the Thomas model (TM) and Yoon–Nelson model (YNM) were applied. The sorption capacity of Bordeaux B on C‐conv and C–FeCl3 was 𝑞TH: (237.88 and 216.21) mg/g, respectively, but the one of Red G was 𝑞TH: (338.46 and 329.42) mg/g. The dye removal (RT) was over 55%. 

Adsorption and Photo-Fenton Degradation of Methylene Blue Using Nanomagnetite/Potassium Carrageenan Bio-Composite Beads

The present study deals with the preparation of nanomagnetite (NM), potassium carrageenan (KC), and nanomagnetite/potassium carrageenan bio-composite beads (NC). Characterization of the prepared solid materials using different physicochemical techniques such as X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscope (TEM), energy-disperse X-ray spectroscopy (EDX), diffuse reflectance spectrophotometer (DRS), swelling ratio (SR%), N2 adsorption, pH of point of zero charges (pHPZC), and Fourier transform infrared spectroscopy (FTIR). Comparing between adsorption and photo-Fenton degradation process for methylene blue (MB) on the surface of the prepared solid materials. Nanomagnetite/potassium carrageenan bio-composite (NC) exhibited high specific surface area (406 m2/g), mesoporosity (pore radius, 3.64 nm), point of zero charge around pH6.0, and the occurrence of abundant oxygen-containing functional groups. Comparison between adsorption and photo-Fenton oxidation process for methylene blue (MB) was carried out under different application conditions. NC exhibited the maximum adsorption capacity with 374.50 mg/g at 40 °C after 24 h of shaking time while 96.9% of MB was completely degraded after 20 min of photo-Fenton process. Langmuir's adsorption model for MB onto the investigated solid materials is the best-fitted adsorption model based on the higher correlation coefficient values (0.9771–0.9999). Kinetic and thermodynamic measurements prove that adsorption follows PSO, endothermic, and spontaneous process, while photo-Fenton degradation of MB achieves PFO, nonspontaneous, and endothermic process. Photo-Fenton degradation is a fast and simple technique at a lower concentration of dye (< 40 mg/L) while at higher dye concentration, the adsorption process is preferred in the removal of that dye.

Photocatalytic removal of diazinon from aqueous solutions: a quantitative systematic review

Diazinon is a widely used pesticide that can be effectively degraded in aqueous solutions via photocatalytic oxidation. This quantitative systematic review was conducted to shed light on the various aspects of photocatalytic diazinon removal based on evidence. A systematic search was performed in Scopus, PubMed, Web of Science, Embase, and Ovid databases with keywords including diazinon, photocatalysis, and their equivalents. The search was limited to original articles in English published between January 1, 2010, and March 25, 2021. The results were expressed by descriptive statistics including mean, SD, median, and percentiles, among others. The initial electronic and manual search retrieved 777 articles, among which 41 studies comprising 49 trials were qualified for data synthesis. The reported diazinon degradation rate ranged from 2 to 100%, with a mean ± SD of 59.17 ± 28.03%. Besides, ZnO/UV, WO₃/UV, TiO₂/UV, and TiO₂/Vis, in sequence, were the most widely used processes with the highest efficacies. Solution pH in the range of 5-8, catalyst dose below 600 mg/L, diazinon initial concentration below 40 mg/L, and contact time of 20-140 min could be the optimum conditions. Diazinon degradation obeyed the first-order kinetic model with k_obs between 0.0042 and 1.86 min^-1 and consumed energy of 38.93-350.36 kWh/m³. Diazoxon and IMP were the most detected by-products of diazinon degradation although bioassay data were scarce. Based on the results, photocatalytic processes are very efficient in removing diazinon from aqueous solutions although more elaborate studies are needed to assess the mineralization rate and effluent toxicity.

Green Synthesis of Nano Zinc Oxide/Nanohydroxyapatite Composites Using Date Palm Pits Extract and Eggshells: Adsorption and Photocatalytic Degradation of Methylene Blue

In this study, zinc oxide nanoparticles (ZnO) and nanohydroxyapatite (NHAP) were prepared in the presence of date palm pits extract (DPPE) and eggshells, respectively. Another four nanocomposites were prepared from ZnO and NHAP in different ratios (ZP13, ZP14, ZP15, and ZP16). DPPE and all nanomaterials were characterized using GC-MS, zeta potentials, particle size distributions, XRD, TEM, EDX, FTIR, and pH_PZC. The characterization techniques confirmed the good distribution of ZnO nanoparticles on the surface of NHAP in the prepared composites. Particles were found to be in the size range of 42.3–66.1 nm. The DPPE analysis confirmed the presence of various natural chemical compounds which act as capping agents for nanoparticles. All the prepared samples were applied in the adsorption and photocatalytic degradation of methylene blue under different conditions. ZP14 exhibited the maximum adsorption capacity (596.1 mg/g) at pH 8, with 1.8 g/L as the adsorbent dosage, after 24 h of shaking time, and the static adsorption kinetic process followed a PSO kinetic model. The photocatalytic activity of ZP14 reached 91% after 100 min of illumination at a lower MB concentration (20 mg/L), at pH 8, using 1.5 g/L as the photocatalyst dosage, at 25 °C. The photocatalytic degradation of MB obeyed the Langmuir–Hinshelwood first-order kinetic model, and the photocatalyst reusability exhibited a slight loss in activity (~4%) after five cycles of application.

Environmental Occurrence, Toxicity Concerns, and Degradation of Diazinon Using a Microbial System

Diazinon is an organophosphorus pesticide widely used to control cabbage insects, cotton aphids and underground pests. The continuous application of diazinon in agricultural activities has caused both ecological risk and biological hazards in the environment. Diazinon can be degraded via physical and chemical methods such as photocatalysis, adsorption and advanced oxidation. The microbial degradation of diazinon is found to be more effective than physicochemical methods for its complete clean-up from contaminated soil and water environments. The microbial strains belonging to Ochrobactrum sp., Stenotrophomonas sp., Lactobacillus brevis, Serratia marcescens, Aspergillus niger, Rhodotorula glutinis, and Rhodotorula rubra were found to be very promising for the ecofriendly removal of diazinon. The degradation pathways of diazinon and the fate of several metabolites were investigated. In addition, a variety of diazinon-degrading enzymes, such as hydrolase, acid phosphatase, laccase, cytochrome P450, and flavin monooxygenase were also discovered to play a crucial role in the biodegradation of diazinon. However, many unanswered questions still exist regarding the environmental fate and degradation mechanisms of this pesticide. The catalytic mechanisms responsible for enzymatic degradation remain unexplained, and ecotechnological techniques need to be applied to gain a comprehensive understanding of these issues. Hence, this review article provides in-depth information about the impact and toxicity of diazinon in living systems and discusses the developed ecotechnological remedial methods used for the effective biodegradation of diazinon in a contaminated environment.

Optimal degradation of organophosphorus pesticide at low levels in water using fenton and photo-fenton processes and identification of by-products by GC-MS/MS

This study aiming to determine the optimal conditions to degrade an organophosphate pesticide diazinon (DZN) at low levels concentrations (μg.mL^-1) and to identify the by-products generated. The degradation processes utilized were the Fenton and photo-Fenton. The iron concentration [Fe²⁺], the hydrogen peroxide concentrations [H₂O₂], and the solution pH are the investigated parameters. The Doehlert three-parameter experimental design was applied to model and optimize both degradation processes. The mathematical models suggested were assessed and validated by application of analysis of variances ANOVA. In the case of Fenton process, the greatest yield of degradation (79%) was obtained at [Fe²⁺] = 35 mg.L^-1 (0.63 mmol.L^-1), [H₂O₂] = 423 mg.L^-1 (12.44 mmol.L^-1), and pH = 5.0. In photo-Fenton process, the maximum yield of degradation (96%) was obtained under the conditions of [Fe²⁺] = 29 mg.L^-1 (0.52 mmol.L^-1), [H₂O₂] = 258 mg.L^-1 (7.59 mmol.L^-1) and pH = 4.6. QuEChERS (quick, easy, cheap, effective, rugged, and safe), as extraction technique, and GC-MS/MS (gas chromatography coupled with triple quadrupole mass spectrometry) were used to identify the by-products degradation of DZN. The identified compounds are diazoxon, triethyl phosphate, triethyl thiophosphate, 2-isopropyl-5-ethyl-6-methylpyrimidine-4-ol, 2-isopropyl-6-methylpyrimidine-4-ol (IMP) and hydroxydiazinon. Three possible pathways for diazinon degradation have been suggested and the hydroxylation, oxidation and hydrolysis are likely probable degradation mechanisms.

Amoxicillin separation from aqueous solution by negatively charged silica composite membrane

Silica composite membranes were successfully prepared by acid/ base-catalyzed sol-gel method and characterized by SEM, FTIR, AFM and contact angle Low isoelectric point of the silica layers provided negatively charged composite membranes, resulting electrostatic repulsion forces between membrane surface and amoxicillin molecules at higher pHs. The rejection rate of amoxicillin was studied systematically at different pHs, solute concentrations, transmembrane pressures and temperatures. It was found that acid-catalyzed membrane has higher amoxicillin rejection ratio compared to base-catalyzed membrane. Especially, acid-catalyzed membrane achieved the highest rejection of 90% at the transmembrane pressure of 6 bar, 45 °C, pH = 10, and initial feed concentration of 50 ppm. Long term stability exhibit that the membrane performance in permeation flux was steady for up to 100 h. However, the AMX rejection of 89% was maintained for over 250 h in acid-catalyzed membrane. It was concluded that the use of negatively charged ceramic membranes is promising for removal of amoxicillin from water resources.

High effective removal of diazinon from aqueous solutions using the magnetic tragacanth-montmorillonite nanocomposite: isotherm, kinetic, and mechanism study

Health and environmental impact of pesticide contamination of groundwater has been reported repeatedly in many studies. The removal of diazinon from agricultural wastewater is still of great interest due to using widely in many developing countries. In the presented study, the magnetic tragacanth-montmorillonite nanocomposite was utilized as an adsorbent to remove diazinon from an aqueous solution. The adsorbent properties were characterized using FE-SEM, EDX, FTIR, XRD, BET, and VSM techniques. The influence of adsorbent dosage, pH, contact time, and initial concentration of diazinon was studied in a batch system. Different adsorption kinetics and isotherm models were used to describe the kinetic and equilibrium data. The results indicated that the adsorption kinetic was fitted better with a Elovich kinetic model, and the adsorption isotherm was well described by the Langmuir-Freundlich model, and the maximum adsorption capacity was 416 mg g^-1. According to Weber and Morris's model and Boyd plot, the results demonstrated that the adsorption kinetic was controlled simultaneously by film diffusion and intraparticle diffusion. Besides, a thermodynamic study showed that the removal of diazinon is an endothermic process. Considering the results, magnetic tragacanth-montmorillonite nanoadsorbent has a high capability to remove diazinon from aqueous solution.

A comprehensive systematic review of photocatalytic degradation of pesticides using nano TiO2

This study has systematically reviewed all of the research articles about the photocatalytic degradation of pesticides using titanium dioxide (TiO₂) nanoparticles (NPs) and ultraviolet (UV) irradiation. Online databases were searched for peer-reviewed research articles and conference proceedings published during 2009-2019, and ultimately 112 eligible articles were included in the review. Fifty-three active ingredients of pesticides and one mixture had been investigated, most of them were organophosphorus (22%), followed by triazine derivatives (11%), chloropyridines (9%), and organochlorines (9%). Sixteen types of TiO₂ with an average photodegradation efficiency of 71% were determined. Based on the type of pesticide and experimental conditions such as irradiation time, the complete photodegradation had been observed. The removal of each group of pesticides has been sufficiently discussed in the article. Effect of experimental conditions on photocatalytic activity has been investigated using linear and polynomial regressions. The strategies to reduce the required energy for this process, doping TiO₂ with metal and non-metal agents, innovative reactor designs, etc., were also discussed. In conclusion, TiO₂ NPs have been successful for degradation of pesticides. Future direction for research incorporates developing and application of heterogeneous doped and immobilized titania having optimized characteristics such as surface area, reactive centers, recombination rate, and phase, and capable to photo-degrade low levels of pesticides residues under solar light in an efficient full-scale size.

Synthesis of carbon nano-onion embedded metal-organic frameworks as an efficient adsorbent for cadmium ions: kinetic and thermodynamic studies

Carbon nano-onions (CNOs), metal-organic frameworks (MOF-199), and carbon nano-onion embedded metal-organic frameworks (CMOF-199) were synthesized from garlic peels as a green source of carbon atoms while MOF-199 was prepared by solvothermal interaction between 1,3,5-benzenetricarboxylic acid and copper nitrate trihydrate. All the prepared solid materials were characterized by nitrogen adsorption/desorption isotherm, transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), X-ray diffraction (XRD), thermogravimetric analysis (TGA), point of zero charge (pH_PZC), and Fourier transform infrared spectroscopy (FTIR). Adsorption of cadmium ions from aqueous solution was investigated onto all prepared solid materials considering different application conditions such as adsorbent dosage, pH, contact time, initial concentration of Cd⁺², and temperature. Adsorption of Cd⁺² was investigated by Langmuir, Freundlich, Temkin, and Dubinin-Radhushkevich adsorption isotherm models. Maximum adsorption capacity (113.3 mg g^-1) was achieved by CMOF-199 at 40 °C. The adsorption of Cd⁺² obeys pseudo-second-order kinetic model. Thermodynamic studies confirmed that the adsorption process is spontaneous, favorable, endothermic, and physisorption. Adsorption results proved that carbon nano-onion embedded metal-organic frameworks are promising solid adsorbents for cadmium ion adsorption.

Novel Removal of Diazinon Pesticide by Adsorption and Photocatalytic Degradation of Visible Light-Driven Fe-TiO2/Bent-Fe Photocatalyst

In the study, Fe was used as a dopant to enhance photocatalytic activity of TiO2. Then, the Fe-doped TiO2 was deposited on bentonite, which was pillared by Fe. The synthesized materials were characterized by SEM, XRD, UV-Vis, BET, and point of zero charge (pHPZC). Then, the synthesized materials were used for diazinon removal under both dark and visible light conditions to investigate adsorption and photocatalytic degradation abilities of the synthesized materials. The maximum diazinon adsorption capacity of the synthesized Fe-TiO2/Bent-Fe was 27.03 mg/g. The obtained results indicated that the Fe-TiO2/Bent-Fe exhibited high photocatalytic degradation activity for removal of diazinon even under visible light. The diazinon removal experiments were also conducted using different photocatalyst dosages, under different pH and light sources to figure the optimal conditions for removal processes. The obtained results indicated that optimal photocatalyst dosage and pH were 0.5 g/L and 4.5, respectively. Finally, the natural light generated from solar could be suitable used for diazinon removal by the synthesized Fe-TiO2/Bent-Fe.