Diatomaceous Research Articles

Diatomaceous earth: radiological characterization and risk assessment

Diatomaceous earth: radiological characterization and risk assessment

Effects of insecticides and repellents on the spread of ‘Candidatus Phytoplasma solani’ under laboratory and field conditions

Recent outbreaks of ‘Candidatus Phytoplasma solani’ resulted in severe losses in potatoes, vegetable crops and grapevines in certain regions of Austria and constituted a major challenge for seed potato production. Therefore, the effects of various insecticides and insect deterrents on pathogen spread were studied both in laboratory and field experiments from 2018 to 2021. In laboratory transmission experiments, field captured Hyalesthes obsoletus were caged on differently treated Catharanthus roseus for five days. The insecticides lambda-cyhalothrin, deltamethrin, esfenvalerate, acetamiprid and chlorpyriphos showed the most rapid impact on insect survival and fully prevented phytoplasma transmission. The particle film forming products kaolin and diatomaceous earth had some effect. A transfer of the promising laboratory results to potato fields, however, was achieved to a limited extent only. Treatments with pyrethroids and acetamiprid every 8–10 days over the flight period of H. obsoletus roughly halved the number of symptomatic plants and tubers in case of moderately susceptible varieties and moderate infection pressure. In the event of susceptible varieties and high disease pressure, treatment effects were hardy discernible. In practical terms, the experiments indicate that insecticide applications alone are not sufficient to mitigate the disease. Spraying of diatomaceous earth and mineral oil did not affect disease incidence in the field.

Mechanical and thermal insulation performance of waste diatomite cement mortar

There are many studies on the application of raw diatomite. Still, there are few studies on using waste diatomite to partially replace cement in concrete, especially in the literature regarding mechanical properties and heat insulation. As such, many waste diatomaceous earths are buried yearly. This study used recycled diatomite to replace part of the cement (10%, 15%, 20%, 30%, 40%) to make mixed cement mortar. Various tests were performed to determine its properties and thermal insulation benefits. According to the results of multiple tests, the amount of replacement diatomite increases the amount of mixing water and setting time. The weight loss and shrinkage rates of the freeze-thaw cycles also increased. However, its water absorption and thermal conductivity decreased. Regarding compressive strength, 10% diatomite substitution had higher strength at 28 days, but 20% diatomite substitution had higher strength at 90 days. The volume change did not exceed the 0.1% critical value specified in ASTM standards. These findings indicate that the most potential results (in terms of mechanical and thermal insulation performance) can be obtained in blends with 20% waste diatomite from the brewing industry.

Modification of Phu Yen diatomite and its application to Cr(VI) removal in aqueous medium

In this study, we successfully prepared a carboxyl-rich carbon nanomaterial from Phu Yen natural diatomite and used it as an effective adsorbent to remove Cr(VI) in aqueous media. The obtained nanomaterial was characterized by means of XRD, SEM, EDS, and FT-IR. The adsorption characteristics of Cr(VI) were investigated. pH has a significant influence on the adsorption process, and pH = 1 is optimal for Cr(VI) adsorption at ambient temperature. Three types of materials were prepared, including natural diatomite (DE), modified diatomite with carbon nanomaterial (DE/S), and modified diatomite with carboxyl-rich carbon nanomaterial (DE/C-S), and DE/C-S exhibits the highest adsorption capacity under the optimal conditions. The pseudo-second-order kinetic model and the Langmuir isotherm well describe the adsorption process of Cr(VI) onto DE/C-S with the maximum adsorption capacity of 58.82 mg·g–1, which is significantly higher compared with that of the natural diatomite (2.29 mg·g–1). Carboxyl-rich carbon-modified diatomite nanomaterials have great potential for use in removing Cr(VI) from wastewater.

Foliar application of Ascophyllum nodosum and diatomaceous earth in the production of cowpea and corn

Cowpea and corn are important as human food, being the guide cowpea, corn acts as a trellis. In these crops it is important to lookfor environmentally friendly alternatives, focused on increasing agricultural yield. The objective of the study was to determine theeffect of the application of two biostimulants, one of Ascophyllum nodosum and the other based on diatomaceous earth on theproduction of pods and grain in cowpea and corn. Cowpea and corn were planted in association in Apatzingán, Michoacán, México.The treatments consisted of the individual application of A. nodosum (AN) and diatomaceous earth (TD) at 0.5, 1.0 and 1.5 g L⁻¹and AN+TD both at doses of 1 g L⁻¹. A randomized complete block design with four replicates was used. It was found that theindividual foliar supply and in combination of the biostimulants, increased green pod yield up to 57 % and grain yield from 32.5 to42.5 %, and also increased morphological variables and yield components. The application of AN, TD and AN+TD in doses of 1 gL⁻¹, caused the highest pod production in cowpea and grain in corn.

Modified Natural Diatomite with Various Additives and Its Environmental Potential.

Diatomite has recently been the subject of intensive scientific research aimed at its extensive use in industry, breeding and agriculture. The only active diatomite mine is in Jawornik Ruski, in the Podkarpacie region of Poland. Chemical pollution in the environment, including that from heavy metals, poses a threat to living organisms. Reducing the mobility of heavy metals in the environment through the use of diatomite (DT) has recently gained much interest. More effective immobilisation of heavy metals in the environment with DT, mainly through the modification of its physical and chemical properties by various methods, should be applied. The aim of this research was to develop a simple and inexpensive material showing more favourable chemical and physical properties compared with unenriched DT in terms of metal immobilisation. Diatomite (DT), after calcination, was used in the study, considering three grain fractions, i.e., 0-1 mm (DT1); 0-0.5 mm (DT2) and 5-100 µm (DT3). Biochar (BC), dolomite (DL) and bentonite (BN) were used as additives. The proportion of DTs in the mixtures amounted to 75%, and of the additive, 25%. The use of unenriched DTs after calcination poses the risk of releasing heavy metals into the environment. Enrichment of the DTs with BC and DL resulted in a reduction or absence of Cd, Zn, Pb and Ni in aqueous extracts. It was found that for the specific surface area values obtained, the additive used for the DTs was of crucial importance. The reduction in DT toxicity has been proven under the influence of various additives. The mixtures of the DTs with DL and BN had the least toxicity. The obtained results have economic importance, as the production of the best quality sorbents from locally available raw materials reduces transport costs and thus the environmental impact. In addition, the production of highly efficient sorbents reduces the consumption of critical raw materials. It is estimated that the savings from producing sorbents with the parameters described in the article can be significant in comparison with popular competitive materials of other origins.

Freeze-thaw resistance of pozzolanic hydrated lime mortars

Degradation of hydrated lime mortars subjected to freezing and thawing is common in historic building conservation. The pozzolanic additions, Argical M1000, diatomite (diatomaceous earth) and brick dust, were evaluated for their ability to improve performance for up to 720 days. Pozzolanic reactions influenced the pore structure evolution, mechanical performance, and chemical reactivity of the mortar matrix. Argical-lime mortars exhibited a sudden failure, while a gradual reduction in mechanical strength was observed for mortars containing brick dust. A slower rate of failure in diatomite mortars was attributed to pore refinement, which was associated with superior freeze thaw performance. This study has advanced the current state of the art regarding how pore structure affects lime mortars' freeze and thaw resistance. Therefore it provides spesifications on how to optimise mortars for historic masonry. A key impact is the more effective use of lime mortars for conservation, thereby protecting heritage structures from degredation.

Optimization of diatom-based blotting materials and their efficient selective adsorption of Pb(II)

In this study, diatom-based Pb(II) imprinted materials (DE/Pb(II)IIP) were synthesized using the surface ion imprinting method with diatomaceous earth as the substrate, 3-mercaptopropyltriethoxysilane (MPTES) as the functional monomer, Pb(II) as the template ion, and glutaric dialdehyde (GA) as the cross-linking agent to solve the pollution problem of Pb(II) ions in water in a targeted and selective manner. The response surface methodology-Box Behnken design was also utilized to analyze the effects of functional monomers, crosslinkers, and polymerization temperature alone, as well as their interaction relationship on the adsorption capacity of the adsorbents and to determine the optimal conditions for adsorbent synthesis. The systematic characterization of the DE/Pb(II)IIP adsorbent materials prior to and after adsorption revealed that MPTES was successfully grafted onto the diatom surface and cross-linked with GA to form uniformly distributed imprinted active sites while avoiding the fundamental problems of self-polymerization and self-cross-linking of functional monomers and crosslinkers. In addition, the combined action of S-Pb coordination and electrostatic adsorption is advantageous for Pb (II) adsorption. The adsorption process followed quasi-second-order kinetics and the Langmuir isothermal adsorption model, as kinetics, isotherm, and thermodynamics demonstrated. The adsorption procedure was governed primarily by homogeneous single-layer chemisorption and was exothermic. DE/Pb(II)IIP exhibited greater selectivity for Pb(II) adsorption than the chemically similar non-imprinted polymer. Excellent selectivity and regeneration properties indicate that DE/Pb(II)IIP is a type of Pb(II) selective recognition adsorption material with a stable structure that can be widely used to recover and utilize heavy metals from actual wastewater.

Rhodamine 6G derivative for the selective copper detection and remediation using nanoporous diatomaceous earth-engineered functional receptor

A rhodamine-derived receptor was synthesized and comprehensively characterized for structural confirmation. The receptor was able to distinguish the copper ions (Cu2+) from other competing cations. The yellow color of the receptor changed to pink upon adding Cu2+ ions, however, other competing cations ions were impotent towards any color variation. The UV–visible titration studies revealed the binding stoichiometry of a 1:1 ratio with a detection limit of 9.663 × 10−8 M. Additionally, a novel idea of the work resides in the use of diatom for the practical application, where the receptor has been tethered on nanoporous diatomaceous earth microparticles (P2D) to remove Cu2+ ions. The results confirmed that 50 mg receptor functionalized DE could adsorb 10 mL of 1 ppm Cu2+ ions from water. Furthermore, a proof-of-concept device that is inexpensive, simple to operate, and continuously removes Cu2+ ions from water has been developed. The efficiency of the device in Cu2+ ion removal could be realized through the naked eye by observing the color change of P2D particles, which has excellent potential for application in remote locations where water contamination is a significant issue.

Preparation of diatomite-based SA@ZIF-8 composite microspheres by electrostatic spray method and its adsorption performance for Cu(II)

Diatomite (DE)-based sodium alginate (SA) loaded ZIF-8 composite microspheres were prepared by high-voltage electrostatic spray technology. SA/DE microspheres were prepared by SA and acid-base-regulated silica sol solution. Ultra-small ZIF-8 was grown on SA/DE microspheres by in-situ synthesis method to obtain ultra-high specific surface area composite microspheres. The morphology and particle size of the composite microspheres were analyzed by SEM, and characterized by FT-IR, XRD and TGA. The optimum adsorption efficiency were achieved by a series of conditions optimization. The adsorption of Cu(II) by SA/DE@ZIF-8 conforms to the Langmuir adsorption model, and the theoretical maximum adsorption capacity is 599.07 mg/g. In summary, this study opens up a new strategy for the design of efficient and easily recycled ZIF-8 composite microspheres for water treatment.

The Potential of Two Entomopathogenic Fungi and Enhanced Diatomaceous Earth Mixed with Abamectin: A Comprehensive Study on Mortality, Progeny Production, Application Method, and Surface Application against Tribolium castaneum.

This study determined the efficacy of Beauveria bassiana (Bals. -Criv.) Vuill., Metarhizium anisopliae (Metchnikoff) Sorokin, and diatomaceous earth mixed with abamectin (DEA) alone and in their combinations for the integrated management of larvae and adults of Tribolium castaneum (Herbst) from three field populations of Pakistan (Multan, Rawalpindi, and Rahim Yar Khan) and one laboratory population (Faisalabad). Treatments were applied on three surfaces, namely, viz. steel, concrete, and jute bags, implementing two application methods, dusting and spraying. The combined treatments were more effective in comparison with single treatments for both larvae and adults. Overall, the highest mortality rates were recorded in the Faisalabad population, followed by the Rehaim Yar Khan, Rawalpindi, and Multan populations. Progeny production was suspended 21 days after exposure to the combined treatment of DEA and both fungi in all populations except Rawalpindi. Larvae were found to be more susceptible than adults in all treatments and intervals. Dusting was more efficient than spraying for both larvae and adults and for all the populations studied. The present study provides a wholistic understanding of the impact of different factors on the success of the combined treatments using DEA and entomopathogenic fungi, supporting their use as surface treatments.

Fabrication of a Floatable Micron-Sized Enzyme Device Using Diatom Frustules.

Immobilization of enzymes has been widely reported due to their reusability, thermal stability, better storage abilities, and so on. However, there are still problems that immobilized enzymes do not have free movements to react to substrates during enzyme reactions and their enzyme activity becomes weak. Moreover, when only the porosity of support materials is focused, some problems such as enzyme distortion can negatively affect the enzyme activity. Being a solution to these problems, a new function "floatability" of enzyme devices has been discussed. A "floatable" micron-sized enzyme device was fabricated to enhance the free movements of immobilized enzymes. Diatom frustules, natural nanoporous biosilica, were used to attach papain enzyme molecules. The floatability of the frustules, evaluated by macroscopic and microscopic methods, was significantly better than that of four other SiO2 materials, such as diatomaceous earth (DE), which have been widely used to fabricate micron-sized enzyme devices. The frustules were fully suspended at 30 °C for 1 h without stirring, although they settled at room temperature. When enzyme assays were performed at room temperature, 37, and 60 °C with or without external stirring, the proposed frustule device showed the highest enzyme activity under all conditions among papain devices similarly prepared using other SiO2 materials. It was confirmed by the free papain experiments that the frustule device was active enough for enzyme reactions. Our data indicated that the high floatability of the reusable frustule device, and its large surface area, is effective in maximizing enzyme activity due to the high probability to react to substrates.

Porous Diatomaceous Earth/Nano-Zinc Oxide Composites: Preparation and Antimicrobial Applications

This paper presents the preparation and characterization of a porous and antimicrobial composite material consisting of diatomaceous earth, an inorganic pore-forming agent, and nano-zinc oxide (ZnO). A modified direct precipitation device produced high-surface area ZnO powder. The effect of reaction temperature, volume flow rate, and titration rate on ZnO particle size was studied. Using sodium chloride, potassium nitrate, and sodium percarbonate as porosity to create porous structures through dissolution was also investigated. This study found that adding cement sand to diatomaceous earth improved mold strength while lowering the volume flow rate, and increasing the reaction temperature increased the specific surface area of ZnO. At 60 °C, the crystalline structure changed from an irregular spherical form to a regular nanorod structure. The specific surface area of the prepared ZnO nanorods reached over 15 m2/g, which is about five times higher. In an antibacterial experiment, adding 5% ZnO nanorods of 50 nm diameter to the porous diatomaceous earth composite material resulted in a nearly 100% antibacterial rate against E. coli in an aqueous environment. The results suggest that the porous diatomaceous earth/nano-ZnO composite has potential applications as an antimicrobial material, and the modified direct precipitation method could have broader implications in materials science.

Effect of modified diatomaceous earth on the heavy metal volatilization characteristics of aged refuse co-combustion

ABSTRACT This paper investigated the adsorption performance of natural and modified diatomaceous earth (DE) for six heavy metal species (Cu, Zn, Ni, Cd, Pb, Cr) during the co-combustion of aged refuse (AR) and municipal solid waste (MSW) in a lab-scale tubular furnace. The aim was to examine the effects of temperature, sorbents, and modification methods on heavy metals’ adsorption performance. The capture rates of calcined diatomaceous earth (CDE) were higher than those of DE, especially for Ni at 700°C, whose capture rate increased to 78.6%. Modified sorbents with NaOH or Na2CO3 significantly reduced the volatility of six heavy metals at 700°C, with the volatilization rates (VR) of Ni and Zn decreasing by at least 50%. Meanwhile, for Cu, Pb, and Zn, the fixation of heavy metals in the bottom ash increased with rising the sorbents mass. However, when the combustion temperature was equal to or above 800°C, the effects of modification on the VR of Cd, Pb, and Zn diminished, except for 10 wt% DE and CDE-10%NaOH. Using NaOH-modified DE at higher temperatures increased the VR of Ni, Pb, and Zn, particularly for Ni whose VR increased by 21.13%. This work contributes to understanding DE’s control mechanism of heavy metals and investigates new heavy metal control strategies during the co-combustion of MSW and AR.

Measurements of Breakdown and Buildup of Thixotropy in Cement Pastes Containing Diatomaceous Earth

This paper proposes a comprehensive series of protocols that can make quantitative measurements on both breakdown and buildup aspects of thixotropic behaviors of cement pastes. While measuring breakdown and buildup separately, the correlations between these two aspects have also been investigated. Cement pastes with different water-to-binder ratios (w/b=0.4, 0.5 and 0.6) and different replacement levels of Diatomaceous Earth (DE) (0%, 2%, 6% and 10% by weight of cement) were studied. To simulate the real on-site conditions, parameters such as pressure and temperature were also considered during the measurement. The research found that increase in DE replacement dosage can reduce the energy required to breakdown thixotropic structure of cement pastes while no specific trend on buildup aspect was observed. Among the three used w/b ratios, the 0.5 w/b ratio has the most reduction effect in breakdown energy, where using 10% DE can lead to 65% of energy reduction in breakdown compared to the control sample. However, the measured yield stress for these specimens were very similar to each other. In addition, increase in temperature significantly increases the buildup ratio of cement pastes while increase in pressure as high as 20 MPa has a minimal impact on thixotropic properties of cement pastes.

Optimization of modified QuEChERS method for extraction of selected pharmaceuticals from vegetable samples using HPLC


 ABSTRACT. Optimized QuEChERS (quick, easy, cheap, effective, rugged and safe) method of sample preparation was employed for five selected pharmaceutical compounds on its advantage of simplicity, less extraction solvent and extraction time. Different parameters affecting the extraction efficiency of the target analyte was optimized. Since QuEChERS was developed for pesticides, uses of the method for pharmaceuticals need modification and evaluation of different parameters. Clean-up sorbents were evaluated for their matrix effect removal after extraction and a combination of d-SPE sorbent, MgSO4, PSA, C18 and diatomaceous earth found to be selective clean-up sorbent for the targeted compounds. The addition and amount of diatomaceous earth and EDTA during the clean-up and extraction steps, respectively, were also examined and the amount was optimized. Solvent type and composition, salt type and extraction time were also optimized and methanol, MgSO4 with NaCl salt and 5 min extraction time was obtained. The method was successfully applied to different vegetable samples collected from Addis Ababa, Ethiopia and Johannesburg, South Africa (carrot, cabbage and lettuce) and none of the target analytes were found in the sample investigated. The matrix effect study on vegetable samples collected was found very high that suppresses the signal during analysis.
 
 KEY WORDS: QuEChERS, EDTA, Pharmaceuticals, Vegetable, HPLC
 Bull. Chem. Soc. Ethiop. 2023, 37(4), 831-844. 
 DOI: https://dx.doi.org/10.4314/bcse.v37i4.3

Phenanthrene sorption studies on coffee waste– and diatomaceous earth–based adsorbents, and adsorbent regeneration with cold atmospheric plasma

Phenanthrene (PHE) is a polycyclic aromatic hydrocarbon categorized as a high priority organic pollutant being toxic for the ecosystem and human health, and its sorption on natural organic or inorganic substances seems a well-promising method for its removal from water streams. The goals of the present work are (i) to assess the capacity of low-cost adsorbents fabricated by treating coffee wastes and diatomaceous earth to remove PHE from water; (ii) to elucidate the role of the pore structure on PHE sorption dynamics; and (iii) to assess the potential to regenerate adsorbents loaded with PHE, by using the novel technology of cold atmospheric plasma (CAP). Diatomaceous earth (DE) and DE pre-treated with sodium hydroxide (NaOH) or phosphoric acid (H3PO4) were chosen as inorganic adsorbents. Coffee waste (CW) and activated carbons (AC) produced from its pyrolysis at 800 °C (CWAC), either untreated (CWAC-800) or pre-treated with NaOH (CWAC-NaOH-800) and H3PO4 (CWAC-H3PO4-800), were chosen as organic adsorbents. The adsorbents were characterized with nitrogen adsorption–desorption isotherms, attenuated total reflectance-Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. Based on the PHE sorption capacity and pore structure/surface characteristics, the CWAC-NaOH-800 was chosen as the most efficient adsorbent for further equilibrium and kinetic sorption studies. The multi-compartment model was used to describe the PHE sorption dynamics in CWAC-NaOH-800 by accounting for the pore/surface diffusion and instantaneous sorption. The CWAC-NaOH-800 exhibited remarkable values for (i) the specific surface area (SBET = 676.5 m2/g) and meso- and micro-pore volume determined by nitrogen sorption (VLN2 = 0.415 cm3/g); (ii) the macro- and meso-pore volume determined by mercury intrusion porosimetry (VMIP = 3.134 cm3/g); and (iii) the maximum PHE sorption capacity (qmax = 142 mg/g). The percentage of adsorbent recovery after its regeneration with CAP was found to be ~ 35%. From the simulation of sorption dynamics, it was found that at early times, the sorption kinetics is governed by the film diffusion towards the external surface of grains, but at late times, most of the adsorbed mass is transferred primarily to meso-/macro-pores via diffusion, and secondarily to micro-porosity via surface diffusion. Based on the adsorbent characteristics, effect of pH on sorption efficiency, and numerical analysis of sorption dynamics, it was concluded that probably the dominant adsorption mechanism is the π-π interactions between hydrophobic PHE aromatic rings and CWAC-NaOH-800 graphene layers. The high PHE removal efficiency of CWAC-NaOH-800, the successful interpretation of sorption dynamics with the multi-compartment model, and the potential to regenerate PHE-loaded adsorbents with the green and economic technology of CAP motivate a strategy for testing CWACs towards the adsorption of other PAHs, application of adsorbents to real wastewaters, and scaling-up to pilot units.Graphical

Effects of poly(butanediol adipate ester) based polyurethane prepolymer content on structure and properties of PLA–diatomaceous earth composites

AbstractDeveloping green composites has received intense attention among the scientific community because of their ability to help alleviate the global environmental pollution challenges. This current work focused on preparing a bio‐based composite material with desirable performance using renewable materials like diatomaceous earth, and polylactic acid (PLA) with poly(butanediol adipate ester) prepolymer (PBAPU) as a compatibilizer. The composites were prepared by reactive mixing using an intensive mixer. Subsequently, the effects of the PBAPU content on the structure and properties of the composites were studied. From the test results, it was revealed that increasing the PBAPU content resulted in an increasing trend in the properties of the composites. For instance, the thermal stability of the composites was improved as the PBAPU content was increased, and the best thermal stability was obtained when 20 wt% PBAPU was added. In addition, the mechanical properties test results showed that the elongation at break and impact strength of the composites increased with increasing PBAPU content. On the contrary, the tensile strength of the composites decreased with increasing PBAPU content. The scanning electron microscope images showed that the compatibility between the PLA matrix and PBAPU in the composites was improved significantly. Based on the analysis of the test results for the material's structure, morphology, thermal stability, fluidity, and other properties, it can be concluded that a bio‐based composite material with desirable performance was successfully prepared.

Efficacy of diatomaceous earth, and entomopathogenic fungi, Beauveria bassiana, and Trichoderma asperellum in combination and separately, against Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae)

BackgroundCallosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) is one of the most significant pests infesting leguminous crops since it is found in tropical and subtropical climates, as well as in Turkey. The most often utilized methods of managing these insects are fumigants and synthetic insecticides. However, chemical pesticides lead to increased risks for human health, chemical residues, insect resistance, and environmental contamination. Therefore, the present study aimed to determine the effectiveness of entomopathogenic fungi [Beauveria bassiana (Bb) and Trichoderma asperellum (Ta)] individually or in combination with diatomaceous earth (DE) against C. maculatus. The fungi Bb and Ta were applied at 1 × 104, 1 × 106 and 1 × 108 spores/kg of chickpea seeds and mixed with 200, 400, 800 mg/kg of DE. Additionally, the progeny production of the insect on chickpea in the different treatments was evaluated after 40 days of exposure.ResultsIn all individual treatments, total adult mortality of the insect was accomplished solely by using the highest DE treatment rate (800 mg/kg) after 7 days. The most effective combination that was a mixture at highest application rate of DE/Bb (800 mg/kg of DE + 1 × 108 spores/kg of Bb) caused 100% mortality after 6 days of exposure and had the lowest LT50 (2.97) and LT90 (5.46) values (days). Although other DE/Bb binary combinations caused 100% mortality of C. maculatus 6 days after treatment, their LT50 and LT90 values were lower. Insect mortalities were 100% in all DE/Ta binary combinations on days 7 and 8, and the highest application rate (800 mg/kg of DE + 1 × 108 spores/kg of Ta) of this combination had the lowest LT50 (4.14) and LT90 (6.17) values (days). Individual treatments of DE, Bb, Ta and their binary combinations caused significant reduction in progeny production after 40 days of treatment compared with progeny production in the control of C. maculatus. The highest progeny production (88.9%) was observed at the highest treatment rate of DE/Bb combinations (800 mg/kg of DE + 1 × 108 spores/kg of BB).ConclusionsThe treatments used in combination of Bb or Ta with DE resulted in increased insecticidal effectiveness against C. maculatus. These natural agents caused considerable decreasing of progeny production of the pest. Even with reduced application rates, the agents with a promising potential against the pest showed acceptable results in binary combinations.

Fabrication of Cu0-composited CuFe2O4 magnetic nanoparticles on diatomite support for efficient degradation of tetracycline hydrochloride by a Fenton-like system

Paramagnetic Cu/CuFe2O4/DE composites were fabricated by a one-step solvothermal method to design a heterogeneous Fenton-like catalyst to degrade tetracycline hydrochloride (TC). The Cu/CuFe2O4/DE were characterized by SEM, TEM, XRD, BET, and XPS methods. The catalytic activity of CuFe2O4 was improved using diatomite and Cu0. Diatomite (DE) enhanced the dispersity of Cu/CuFe2O4, minimized metal ions leaching, and improved stability. The Cu0 is used for the regeneration of Fe3+. The synergy between Cu+/Cu2+ and Fe2+/Fe3+ redox pairs promotes hydroxyl radical production upon H2O2 decomposition. The synthesized materials were characterized by SEM, TEM, XRD, BET, and XPS, and their catalytic activities were discussed and analyzed. 95.5 % TC was degraded within 90 min (initial conditions, pH = 5.0 and [TC] 50 mg/L), and showing excellent anti-interference ability to the presence of SO42-, Cl-, NO3-, CO32- and humic acid (HA).The presence of active species, viz., •OH and •O2- radicals generated in the Cu/CuFe2O4/DE/H2O2 system were detected by ESR quenching measurements. The •OH and •O2- mediated TC degraded pathways were proposed using the intermediates identified by LC-MS data. The novel heterogeneous Fenton-like process developed using Cu/CuFe2O4/DE/H2O2 is robust for TC degradation as exemplified in its stability and reusability measurements.