Oil-contaminated soils resulted from drilling activities can cause significant damages to the environment, especially for living organisms. Treatment and management of these soils are the necessity for environmental protection. The present study investigates the field study of seven oil-contaminated soils treated by different stabilization/solidification (S/S) methods, and the selection of the best treated site and treatment method. In this study, first, the ratios of consumed binders to the contaminated soils (w/w) and the treatment times for each unit of treated soils were evaluated. The ratios of consumed binders to the contaminated soils were between 6 and 10% and the treatment times for each unit of treated soils were between 4.1 and 18.5 min/m³. Physicochemical characteristics of treated soils were also determined. Although S/S methods didn’t change the water content of treated soils, they increased the porosity of soils. Unexpectedly, the cement-based S/S methods didn’t increase the pH of the treated soils. The highest and the lowest leaching of petroleum hydrocarbons was belonging to S/S using diatomaceous earth (DE) and the combination of Portland cement, sodium silicate and DE (CS-DE), respectively. The best acid neutralization capacity was obtained for soils treated using the combination of Portland cement and sodium silicate (CS). Based on the best-worst multi-criteria decision-making method (BWM-MCDM), the soils treated using CS-DE was select as the best. The BWM-MCDM can be used as an effective tool for the selection of the best alternative in all areas of environmental decontamination.

The N-TiO2/g-C3N4@diatomite (NTCD) composite has been prepared through a simple impregnation method, using titanium tetrachloride as precursor and urea as nitrogen-carbon source. Then the effects of calcination temperature on structure, surface property and photocatalytic activity of the catalysts were investigated. And XRD, TEM, XPS, FTIR and UV–vis diffuse adsorption spectroscopy were used to characterize the obtained powders. The photocatalytic activity of the NTCD was evaluated through the reduction of aqueous Cr (VI) under visible light irradiation (λ > 400 nm). The results demonstrated that the nano-TiO2 particles ranging from 15 to 30 nm in the crystal of anatase are well deposited on the surface of diatomite in the NTCD-500 which calcined at 500 °C for 2 h. Furthermore, the g-C3N4 with the lay thickness of 0.92 nm was attached to the surface of nano-TiO2. The N-doped TiO2 and g-C3N4 doped catalysts could co-enhance response in the visible light region and reduce band gap of NTCD-500 (Eg = 3.07 eV). And the NTCD-500 sample exhibited nearly 100% removal rate within 5 h for photocatalytic reduction of Cr (VI) which was higher activity than P25, crude TiO2@diatomite and g-C3N4@diatomite.

Three types of diatomite-based adsorbents—diatomaceous earth (DE), purified diatomite (PD), and diatomite@MgO/CaO (D@MgO) were used for adsorption decontamination of ammonium from Lake Qarun water (28.7 mg/L). The adsorption properties of the three diatomite-based adsorbents were evaluated by both batch and fixed-bed column adsorption studies. The kinetic results demonstrated removal percentages of 97.2%, 69.5%, and 100% using DE, PD, and D@MgO, respectively, at a 1 g/L adsorbent dosage. The adsorption results using DE and D@MgO showed the best fitness with pseudo-first-order kinetic and Langmuir isotherm models, while the obtained results using PD demonstrate better fitness with the Freunlidich model. The recognised fitting results with the pseudo-first-order model and estimated adsorption energies demonstrated physical uptake of ammonium by DE (5.93 kJ/mol), PD (4.05 kJ/mol), and D@MgO (7.81 kJ/mol). The theoretical maximum ammonium uptake capacity of DE, PD, and D@MgO were 63.16 mg/g, 59.5 mg/g, and 78.3 mg/g, respectively. Using synthetic adsorbents in a fixed-bed column system for treating ammonium ions in Lake Qarun water resulted in removal percentages of 57.4%, 53.3%, and 62.6% using a DE bed, PD bed, and D@MgO bed, respectively, after treating approximately 7.2 L of Lake Qarun water using a bed thickness of 3 cm, a flow rate of 5 mL/min, pH 8, and the determined ammonium concentration in Lake Qarun water (28.7 mg/L). The curves demonstrated breakthrough times of 900 min, 900 min, and 960 min for the DE bed, PD bed, and D@MgO bed, respectively, with 1440 min as the saturation time. The columns’ performances also were studied based on the Thomas model, the Adams-Bohart model, and the Yoon-Nelson model.

The insecticidal activity of the Diatomaceous Earth (DE) of Sig was assessed against the Dermestes haemorrhoidalis, which is the main pest affecting wheat stored in Blida, a central region of Algeria and one of the four cereal regions managed by the Algerian Inter-branch Cereals Office (AICO). The formulation was tested at two different doses: 500 and 1000 ppm against adults of the species. The bioassays were carried out in 1-litre glass jars containing soft wheat with an average moisture content of 60% mixed with diatomaceous earth and maintained at 27°C and 70% of humidity. The effectiveness of the treatment was assessed by recording adult mortality after 2, 7 and 14 days. Sig’s diatomite showed significant insecticidal activity against Dermestes haemorrhoidalis after only two days of treatment with both doses 500 and 1000 ppm. After 14 days, average mortality was more than 95% even at 500 ppm. Furthermore, electron microscopy of the diatomite particle from Sig (Algeria) reveals the architecture of the frustule. It shows a porous and brittle siliceous shell made largely of diatomite “skeletons”. This research work allowed getting insights into the mechanism of action of diatomite on the Dermestes haemorrhoidalis. On the other hand, the identification of diatomite of Sig was performed by X-ray diffraction and infrared.

This research analyzes the behavior of different diatomite from Peru, and their potential use for the removal of heavy metals from contaminated effluents. Seven different diatomites were characterized by X-ray diffraction, X-ray fluorescence, scanning electron microscopy, specific surface area, and cation exchange capacity. The absolute removal and the removal efficiency of Cu, Pb, and Zn were assessed by stirring the diatomite in solutions of known concentration of the contaminant, and then analyzing the solutions by atomic absorption spectroscopy (AA). The results were finally correlated with microstructural, chemical, and physicochemical characteristics of the diatomites. It was found that Peruvian diatomites have potential use for decontamination of heavy metals from contaminated effluents even with their low SiO₂ content. Affinity for the studied metals was as follows: Zn > Pb > Cu, with removal percentages as higher than 98% for Zn. No one-to-one relationships were found between the removal efficiency of the studied metals with properties of diatomites. Different parameters must be taken into account at the same time to understand the efficiency of metal removal in polluted waters. In this case, the specific surface area and minor oxides have the greatest effect on the removal efficiency of all metals.

In the present study, we evaluated the insecticidal efficacy of diatomaceous earth (DE) and pirimiphos-methyl for the control of phosphine-susceptible and phosphine-resistant populations of Tribolium castaneum (Herbst) and Sitophilus oryzae (L.). Insecticides were applied on wheat or rice at two doses: DE was applied at 1000 and 2000 ppm and pirimiphos-methyl at 1 and 5 ppm. Adult mortality was measured after 7, 14, and 21 days of exposure, and progeny production capacity on the treated substrates was evaluated 65 days later. For T. castaneum, we found that DE, at 2000 ppm, was able to provide 100% control of two of the three populations tested, while for the third population mortality reached only 84%. Similarly, there were differences in mortality levels after exposure to DE-treated grains between the two S. oryzae populations tested. At 1 ppm, pirimiphos-methyl was not effective for any of the T. castaneum populations tested, but complete mortality was recorded for all populations at 5 ppm. In general, populations of S. oryzae were more susceptible than those of T. castaneum, for both commodities. Our data indicate that both insecticides can be used with success in phosphine resistance management programs, but there are populations of a given species that may be less susceptible, which constitutes a preliminary screening essential.

Mechanically robust Fe₃O₄/porous carbon/diatomite composite monolith was prepared from waste corrugated cardboard box and diatomite via slurrying in FeCl₃ solution, dewatering, molding, and carbonization at 600 °C. The products were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (SEM), N₂-adsorption/desorption, Raman spectroscopy, and ultraviolet-visible-near-infrared (UV-Vis-NIR) spectroscopy. The water wettability, photothermal conversion property, and solar steam generation performance of the products were also evaluated. Results showed that the presence of FeCl₃ led to the formation of more pores and magnetic Fe₃O₄ crystallites, while diatomite provided good hydrophilicity for the composite. The product exhibited light absorption above 65% within the wavelength ranging from 200 to1974 nm, and its surface temperature eventually increased by 30 °C under 0.25 sun irradiation due to photothermal effect. Moreover, solar steam yield under 0.25 sun irradiation for 3600 s was improved by 67% with the presence of the monolithic composite because of the occurrence of interfacial solar steam generation and heat transfer from the composite acted as a heat island.

The development of powdery photocatalyst has long been studied, yet the low recovery in water is still its bottleneck. In this work, magnetic recyclable lanthanum-doped TiO₂/copper ferrite/diatomite (La-TCD) ternary composite was synthesized via sol-gel method. The physicochemical properties of various hybrid catalysts were characterized and studied, and their photocatalytic properties were evaluated via the decomposition of antibiotic oxytetracycline and disinfection of bacteria Escherichia coli under visible light. The formation of heterojunction between La-doped TiO₂ and copper ferrite hindered the recombination of photo-induced charge carriers and improved the photocatalytic activity. The photodecomposition rate of OTC was accelerated by the high adsorption ability of diatomite, due to the adsorption and decomposition synergistic effect between catalysts and substrate diatomite. The optimal La dopant amount as well as optimal catalyst dosage was determined. The composite could simply be recovered from waterbody via an external magnet, and the repetition tests indicated no obvious decrease of photoactivity. This nanocomposite presented good potential to be applied in environmental remediation process, due to its high photocatalytic efficiency under visible light, as well as its good reusability and stability.

A waste–struvite/diatomite compound (MAP@Dia) recovered from nutrient-rich wastewater treated by MgO-modified diatomite (MgO@Dia) was provided to immobilize lead in aqueous solution and contaminated soil. The mechanism and effectiveness of lead immobilization was investigated, and the pHₛₜₐₜ leaching test and fixed-bed column experiments were carried out to assess the risk of MAP@Dia reuse for lead immobilization. The results showed that MAP@Dia were effective in immobilizing lead in aqueous solution with adsorption capacity of 832.47–946.50 mg/g. The main mechanism of Pb immobilization by MAP@Dia could be contributed by surface complexation and dissolution of struvite followed by precipitation of hydroxypyromorphite Pb₁₀(PO₄)₆(OH)₂. Lead(II) concentration reduced from 269.61 to 78.26 mg/kg, and residual lead(II) increased to 53.14% in contaminated soil when the MAP@Dia application rate was 5%. The increased neutralization capacity (ANC) and lower lead extraction yields in pHₛₜₐₜ leaching test in amended soil suggested 5 times of buffering capacity against potential acidic stresses and delayed triggering of “chemical time bombs.” The results of column studies demonstrated that amendment with MAP@Dia could reduce the risk of lead and phosphorus (P) leaching. This study revealed that MAP@Dia could provide an effective solution for both P recycling and lead immobilization in contaminated soil.

An innovative diatomite-supported iron catalyst has been developed by using an impregnation process with a mixture of ferrous (Fe²⁺) and ferric (Fe³⁺) ions in the form of precipitated iron hydroxides. Raw and modified diatomite samples have been characterized by X-ray fluorescence and scanning electron microscopy. The main characterization results have revealed that modified diatomites are amorphous and have higher iron concentrations than raw diatomite. The results also indicate that the modified materials provided significant catalytic activity on phenanthrene degradation by using sodium persulfate. Satisfactory results were obtained with 45 g/L of sodium persulfate and 1 g of modified diatomite, thus degrading 98% of phenanthrene during 168 h of treatment. Kinetic and statistical approaches were developed for the remediation process herein, which have been validated with experimental data, thence yielding suitable results.