High Degree Of Mineralization Research Articles

Scanning electron microscopy and energy-dispersive X-ray spectroscopy on the degree of bone mineralization at the bone-implant interface

Background. The purpose of this research was to evaluate the degree of mineralization as well of the chemical composition at the interface of failed dental implants with surrounding bone. Material and methods. The analysis was performed on human histological samples by the aid of a scanning electron microscope and an energy-dispersive x-ray spectroscopy (ESEM-EDX). Results. The middle and the apical region of the implant surfaces had higher quantity of bone tissue deposition. A higher degree of mineralization was observed in these two regions as well. Conclusion. From the analysis performed by the aid of scanning electron microscopy, it appears that the bone tissue deposition is better represented in the middle and apical region of the implants.

Cu-Fe nanoparticles decorated rice hull/chitosan@FeAl2O4 to boosted peroxidase-like activity for catalytic degradation of antibiotics: Kinetics and mechanistic insights

A series of derived magnetic porous carbon skeleton-coated Cu/Fe nanocomposites (CunFe1-n@CRH-x) were synthesized using chitosan-rice hull waste-hercynite by an injection molding and impression method, which is introduced as a “treating wastewater by waste residuals” for environmental-friendly remediation. Specifically, the CRH-x is a unique platform for the growth of uniformly dispersed metal oxides with high catalytic performance. After that, the morphological and structural features of post-synthesized nanocomposites were fully identified by applying alternative analytical and spectroscopic tools. The peroxidase-like activity of catalysts via electron transfer process between the simultaneously surface-activated H2O2 and target contaminants (e.g., tetracycline (TC), naproxen (NPX), ciprofloxacin (CIP), and paracetamol (PC)) were evaluated in detail. In the following, to find interrelationships between catalytic performance and structural characteristics, environmental parameters, ions interface, long-term stability, reusability, removal pathway, and universality of the system in various water sources were investigated in detail. The excellent peroxidase-like activity of Cu0.6Fe0.4@CRH-400 can be related to the high Brønsted acid intensity, small pore size, high surface area, and dual-synergy of Cu-Fe nanocatalyst and H2O2. The Cu0.6Fe0.4@CRH-400 can be boosted electron transfer via the dual redox cycle of Cu2+/Cu+/Cu2+ and Fe3+/Fe2+/Fe3+ under its core–shell scaffold, which promoted the generation and/or conversion of active species (•OH2, O2•-) to •OH. 98.20 % of TC, 93.90 % of NPX, 92.10 % of CIP and 100 % of PC were degraded through a rate constant (and TOC (%) removal) of 0.0838 min−1 (51.10 %), 0.0897 min−1 (46.5 %), 0.0737 min−1 (42.30 %), and 0.1168 min−1 (54.6) in Cu0.6Fe0.4 @CRH-400/H2O2 system, respectively, which confirmed that the remediation follows pseudo-1st-order kinetic model. Additionally, the low activation energy of 22.04 kJ/mol and favorable ΔH (−19.60 kJ/mol) of TC degradation confirmed the effectiveness of the catalytic system. Importantly, the reaction pathway was proposed and then predicted the acute toxicity (oral LD50) and mutagenicity of the degradation intermediates. The fairly high degree of mineralization, high anti-interferences, broad-spectrum remediation capacity, adaptability to predominant environmental conditions, and wide pH range (3.0–9.0) by Cu0.6Fe0.4 @CRH-400/H2O2 system in the various real water matrices further endorsed the superiority of the catalytic system.

Experimental Early Stimulation of Bone Tissue Neo-Formation for Critical Size Elimination Defects in the Maxillofacial Region.

A biomaterial is proposed for closing extensive bone defects in the maxillofacial region. The composition of the biomaterial includes high-molecular chitosan, chondroitin sulfate, hyaluronate, heparin, alginate, and inorganic nanostructured hydroxyapatite. The purpose of this study is to demonstrate morphological and histological early signs of reconstruction of a bone cavity of critical size. The studies were carried out on 84 white female rats weighing 200-250 g. The study group consisted of 84 animals in total, 40 in the experimental group and 44 in the control group. In all animals, three-walled bone defects measuring 0.5 × 0.4 × 0.5 cm3 were applied subperiosteally in the region of the angle of the lower jaw and filled in the experimental group using lyophilized gel mass of chitosan-alginate-hydroxyapatite (CH-SA-HA). In control animals, the bone cavities were filled with their own blood clots after bone trepanation and bleeding. The periods for monitoring bone regeneration were 3, 5, and 7 days and 2, 3, 4, 6, 8, and 10 weeks. The control of bone regeneration was carried out using multiple morphological and histological analyses. Results showed that the following process is an obligatory process and is accompanied by the binding and release of angiogenic implantation: the chitosan construct actively replaced early-stage defects with the formation of full-fledged new bone tissue compared to the control group. By the 7th day, morphological analysis showed that the formation of spongy bone tissue could be seen. After 2 weeks, there was a pronounced increase in bone volume (p < 0.01), and at 6 weeks after surgical intervention, the closure of the defect was 70-80%; after 8 weeks, it was 100% without violation of bone morphology with a high degree of mineralization. Thus, the use of modified chitosan after filling eliminates bone defects of critical size in the maxillofacial region, revealing early signs of bone regeneration, and serves as a promising material in reconstructive dentistry.

Optimization of Visible-Light-Driven Ciprofloxacin Degradation Using a Z-Scheme Semiconductor MgFe2O4/UiO-67.

A heterogeneous photocatalyst, MgFe2O4/UiO-67 (MU-x), was successfully synthesized by doping magnetic magnesium ferrite nanoparticles (MgFe2O4) with the UiO-67 metal-organic framework at various weight ratios (MgFe2O4: UiO-67 at 30, 50, 70, and 90 wt %). Various techniques, including X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared spectroscopy (FT-IR) , Brunauer-Emmett-Teller (BET), photoluminescence (PL), vibrating sample magnetometry (VSM), electrochemical impedance spectroscopy (EIS), and ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), were used to characterize the prepared photocatalysts. The photocatalytic performance of MU-x in the degradation of ciprofloxacin (CIP) under visible light was assessed. The CIP degradation efficiency was found to increase as the amount of MgFe2O4 in the composite was increased up to 70 wt %. Experimental conditions were optimized using response surface methodology (RSM) based on central composite design (CCD) with three factors: initial pH, catalyst loading, and CIP concentration. Using the obtained model, the optimal conditions were determined as follows: initial pH of 8.025, catalyst loading of 33.8 wt %, and CIP concentration of 10.8 mg/L. Under these optimal conditions, a notable improvement was achieved, with 99.62% of CIP removal achieved within 90 min, surpassing the performance of previously reported photocatalysts. Total organic carbon (TOC) analysis revealed a high degree of mineralization, at 81.25%. The degradation pathway of CIP was investigated based on liquid chromatography-mass spectrometry (LC-MS) analysis. Finally, the values of ECB and EVB of the photocatalyst were determined and the possible degradation mechanism of CIP was investigated based on Mott-Schottky and the applied scavengers. The hydroxyl radical (•OH) was identified as the dominant species in the removal of CIP through a trapping experiment. The photocatalyst with 70 wt % of MgFe2O4 (MU-70) exhibited excellent stability and recoverability with an external magnet, demonstrating 86.33% CIP removal after four cycles. According to the obtained results, MU-70 is a promising visible-light-active photocatalyst with great potential for water treatment applications and convenient recovery.

Peroxymonosulfate-based catalytic degradation of reactive dyes in real wastewater by Fe/N-codoped carbocatalysts loaded on carbon cloth

This study simulated actual dyeing wastewater in dyeing factories with three types of dyeing wastewaters from laboratory cotton fabric dyeing to investigate the effects of catalyst and oxidant peroxymonosulfate (PMS) concentrations, pH level, and temperature on dye degradation in wastewater and determine the optimal conditions for dyeing wastewater treatment accordingly. The results demonstrated that the optimal conditions varied with the reactive dyes. Specifically, the optimal oxidant PMS concentration for degrading Reactive Yellow and Reactive Blue was 0.6 g/L, and that for degrading Reactive Red was 0.4 g/L. The optimal pH level for degrading Reactive Red and Reactive Blue was around 7.0, and that for degrading Reactive Yellow was about 5.0. The activation energy of the degradation and the mineralization degree of the three dyes were also discussed. Reactive Blue showed greater activation energy (47.0 kJ/mol) and a higher mineralization degree (81% chemical oxygen demand removal) than the other two dyes under optimal disposal conditions. The Fe/N-codoped carbocatalyst loaded on carbon cloth exhibited desirable reusability and good stability for the degradation of the three dyes. Mechanisms involved in their degradation were analyzed through X-ray photoelectron spectroscopy, focusing on N species, Fe-N binding, and C=C and C–N active components in the Fe/N-codoped carbocatalyst. Electron paramagnetic resonance experiments demonstrated that both the radical and non-radical pathways were accountable for the degradation of the three dyes, primarily the non-radical pathway. This study may contribute to the application of activated PMS for practical dyeing wastewater treatment.

Using PCA and ANN in the explanation of groundwater chemism. Case of the Messaad Plateau. South Algerian Steppe Region

The objective of this work is to study the chemistry of groundwater in the messaad plateau which is located 300km south of the capital of Algiers. The results obtained showed that the waters are very strongly mineralized overall, with a predominance of calcium sulphate facies and calcium chloride facies. a high degree of mineralization in the South and South-East part of the study area near Oued Messaad. The Principal Component Analysis (PCA) has shown that the increase in mineralization is mainly due to the dissolution of evaporative mineral-rich salt-bearing formations. The hydro-chemical model based on Artificial Neuron Networks (ANN) of the multilayer perceptron (MLP) type has shown that the SO4 2-,Cl- ,Ca2+,Na+ ions are the most important factors influencing the electrical conductivity of water. These ions are the result of the dissolution of gypsum and halite continuously in the clays and marls of the Barremian formations.

ENGINEERING AND GEOLOGICAL STUDIES OF THE TENGIZ DEPOSIT

In this article, a study of geological and ecological loads on the geological environment at the Tengizfield, located in the Zhyloy district of Atyrau region of the Republic of Kazakhtan, is carried out. Soil tests by dynamic sounding (STDS) were performed on all drilling wells for sandy soils. In the process of performing engineering and geological exploration, static sounding of soils was performed at the projected sites of GDP-1 (gas distribution plant) and Torch, with the measurement of hydrostatic pore pressure. Physical and mechanical properties of soils, chemical properties of soils and chemical properties of groundwater were determined during laboratory studies. In the studied territory, the soils composing the engineering-geological section to a depth of up to 25 m are saline with an average degree of salinity. All lithological-facies groups of soils also contain a significant amount of carbonates and gypsum in their composition. For loamy silt (IGE-1b), according to the combination of physico-chemical and mechanical characteristics (fluid consistency, high degree of salinity, high degree of compressibility and low strength, the possibility of manifestation of thixotropic properties under dynamic influences), this soil belongs to the category of weak water-saturated clay soils. Weak soil (IGE-1b) is observed at a shallow depth in some areas. The available geotechnical data is not enough to accommodate areas of weak soils. At the same time, heavy sandy loam (IGE1a) and light sandy clay (IGE-8) have swelling properties of a weak degree. Chemical analysis of groundwater samples taken within the studied territories showed a high degree of mineralization, groundwater belongs to the brackish group, a subgroup of strongly brackish waters. Dangerous geological processes that could negatively affect the construction conditions are characterized by the processes of secondary salinization of soils.

Recovery of lithium from brine with different degrees of mineralization by resorcinol/urea–formaldehyde foam-supported H2TiO3

With the development of new energy industry, the extraction of lithium from liquid minerals has attracted extensive attention. Herein, a novel phenolic resin-supported H2TiO3 foam (RF/UF-HTO) was developed for Li+ recovery from aqueous solutions. It was found that when the thermosetting phenolic resin was modified with urea and then foamed by petroleum ether with boiling points of 60 ∼ 90 °C under the assistance of 1.5% Tween 80 + 3% sodium dodecyl sulfate, the material presented a porous 3D network structure with a high specific surface area and porosity. The maximum adsorption capacity of the material reached 52.41 mg·g−1. The adsorption rate was controlled by the particle diffusion, and the adsorption was proven to be an endothermic process by the microcalorimetry. The material exhibited high adsorption performance for low-concentration Li+ in geothermal water with a low degree of mineralization. The adsorption capacity reached 21.50 mg·g−1 after only 6 h, and the attenuation of adsorption capacity was only 1.96 mg·g−1 after 10 cycles. Because of the high Mg2+ concentration and high degree of mineralization, the adsorption capacity for Li+ in salt lake brine was low. This problem was successfully solved by regeneration with Ba(OH)2, by which the adsorption capacity was enhanced from 0.54 to 20.72 mg·g−1. Even for the fixed-bed adsorption, the adsorption capacity still reached 8.5 mg·g−1. Based on these excellent properties, the material and method developed in this work can be used for Li+ recovery from brine with different degrees of mineralization and composition.

Methylene blue Photo-degradation on the Hetero-junction system α-Fe2O3 / BaTiO3 under sunlight

In recent years, great efforts have been devoted to the development of photocatalysis based on semiconductors for the purification of water and air, on the one hand by the synthesis of these materials by simple, rapid processes and economical and on the other hand by improving their photo-activity essentially by doping process. In this respect, we are interested in improving the photocatalytic activity of Barium Titanate (BaTiO3) under solar irradiation. The perovskite BaTiO3,the hematite α-Fe2O3,and the hetero-junctionα-Fe2O3/BaTiO3synthesized by chemical route were characterized by X-ray diffraction, scanning electron microscopy (SEM), and photo-electrochemistry. These materials have been successfully tested as photocatalysts in the photodegradation of Methylene Blue (MB) under sunlight. The hetero-junctionα-Fe2O 3/ BaTiO3showed enhanced photo-activity compared to end members BaTiO3 orα-Fe2O3.The photo-catalyst nature and its dose, initial MB concentration (Co), and pH were optimized. 20 ppm of MB was completely eliminated after 3 h of exposure to solar irradiation at pH ∼ 11 on α-Fe2O3(15 %)/BaTiO3. A high mineralization degree was confirmed with total organic carbon (TOC) and the results of the quenching test showed that the O2•- radical is the main active specie responsible for the photo-degradation of MB. The kinetic analysis suggested that the MB degradation obeys a pseudo-first-order with a rate constant of1.4 × 10−2min−1 (t1/2 = 50 min). The results were ascribed to the synergistic effect of the hetero-junction α-Fe2O3/BaTiO3, which plays a crucial role in enhancing the electron transfer and thereby in the MB photo-mineralization with elimination rate of 93 %.

Experimental study of sandstone stress sensitivity under different fluids: Characteristics and mechanisms

Stress sensitivity is the phenomenon of permeability variation that caused by pore throat changes, opening or closure of fractures under forces, which is an important parameter in reservoir evaluation. Fractured sandstones under various fluids will produce different stress sensitivity, which can greatly influence oil and gas development. However, little is known on this topic currently. Hence, in this study, characteristics and mechanisms were investigated based on a series of experiments and theoretical analysis. The results indicate that: I, compared with unfractured rocks, fractured rocks show a stronger stress sensitivity. The permeability shows an obvious “decrease initially steep and finally gentle” pattern with the increase of effective stress. II, from purified water to low NaCl/CaCl2 mineralization fluids, the permeability damage of fractured rocks decreases gradually with the increase of mineralization degree; however, it increases with mineralization degree when rocks are under high mineralization fluids, and the damage degree is also high. The permeability damage degree is generally low when fractured rocks are under the action of kerosene. Mechanism analysis indicates that: I, fractured rocks have both fracture and pore systems, whose opening and closure can produce stronger stress sensitivity and more obvious nonlinear variation of permeability than unfractured rocks. II, under purified water conditions, the expansion of clay minerals is an important indicator and reason for the permeability damage. III, under low fluid mineralization degree conditions, the reaction between fluids and minerals will destroy rock structures, increase fracture aperture, and produce secondary pores, and finally decrease the permeability damage to a certain extent. IV, under high fluid mineralization degree conditions, crystals may be deposited, blocking up pores/fractures and producing high permeability damage. V, there are no reactions between minerals and kerosene, hence, the permeability damage degree is generally low. The results are expected to provide references for the exploration and development of fractured tight reservoirs in Kuqa Depression.

Ultrasonication for removal of organic micropollutants from water

This review collects the most theoretical and experimental data about the fundaments of ultrasonic cavitation and its application in the domain of water and drinking water treatment. It is describing the most important mechanism of acoustic cavitation based on "Hot spot theory" which is based on free radicals, especially hydroxyl radicals. The experimental examples are focused on organic micropollutants removal from wastewater and drinking water. There are many organic pollutants resistant to classical treatment flows in wastewater and drinking water treatment plants which means there must be updated with new technologies like Advanced Oxidation Processes (AOPs). Ultrasonication and advanced ultrasonication is one of these new approaches. Ultrasonication was the base of a new chemistry domain - sonochemistry and its development led to new and modern degradation methods of natural and industrial organic pollutants: natural organic matter, phenols, organochlorinated compounds, surfactants, etc. with high mineralization degree. Some examples are described below.

Assessing the Effect of Intensive Agriculture and Sandy Soil Properties on Groundwater Contamination by Nitrate and Potential Improvement Using Olive Pomace Biomass Slag (OPBS)

The relationship between agricultural activities, soil characteristics, and groundwater quality is critical, particularly in rural areas where groundwater directly supplies local people. In this paper, three agricultural sandy soils were sampled and analyzed for physicochemical parameters such as pH, water content, bulk density, electrical conductivity (EC), organic matter (OM), cation exchange capacity (CEC), and soil grain size distribution. Major and trace elements were analyzed by inductively coupled plasma-optical emission spectrometry (ICP/OES) to determine their concentrations in the fine fraction (FF) of the soils. Afterward, the elemental composition of the soils was identified by X-ray powder diffraction (XRD) and quantified by X-ray fluorescence (XRF). The surface soil characteristics were determined by the Brunauer–Emmett–Teller (BET) method, whereas the thermal decomposition of the soils was carried out using thermogravimetric analysis and differential scanning calorimetric (TGA-DSC) measurements. The morphological characteristics were obtained by scanning electron microscopy (SEM). Afterward, column-leaching experiments were conducted to investigate the soil’s retention capacity of nitrate (NO−3). Parallelly, a chemical and physical study of olive pomace biomass slag (OPBS) residue was carried out in order to explore its potential use as a soil additive and improver in the R’mel area. The OPBS was characterized by physicochemical analysis, assessed for heavy metals toxicity, and characterized using (XRD, XRF, SEM, and BET) techniques. The results show that the R’mel soils were slightly acidic to alkaline in nature. The soils had a sandy texture with low clay and silt percentage (&lt;5% of the total fraction), low OM content, and weak CEC. The column experiments demonstrated that the R’mel irrigated soils have a higher tendency to release large amounts of nitrate due to their texture and a higher degree of mineralization which allows water to drain quickly. The OPBS chemical characterization indicates a higher alkaline pH (12.1), higher water content (7.18%), and higher unburned carbon portion (19.97%). The trace elements were present in low concentrations in OPBS. Macronutrients in OPBS showed composition rich in Ca, K, and Mg which represent 10.59, 8.24, and 1.56%, respectively. Those nutrients were quite low in soil samples. Both XRD and XRF characterization have shown a quasi-dominance of SiO2 in soil samples revealing that quartz was the main crystalline phase dominating the R’mel soils. Oppositely, OPBS showed a reduced SiO2 percentage of 26,29% while K, Ca, and P were present in significant amounts. These results were confirmed by XRF analysis of OPBS reporting the presence of dolomite (CaMg, (CO3)2), fairchildite (K2Ca (CO3)2), and free lime (CaO). Finally, the comparison between the surface characteristic of OPBS and soils by BET and SEM indicated that OPBS has a higher surface area and pore volume compared to soils. In this context, this study suggests a potential utilization of OPBS in order to (1) increase soil fertility by the input of organic carbon and macronutrients in soil; (2) increase the water-holding capacity of soil; (3) increase soil CEC; (4) stabilize trace elements; (5) enhance the soil adsorption capacity and porosity.

Efficient mineralization of sugar industry wastewater by catalytic wet air oxidation as an eco‐friendly method and its kinetic modelling

AbstractIn this study, catalytic wet air oxidation using lanthanum cobalt oxide (LaCoO3) as catalyst was employed for the efficient treatment of synthetic sugar industry wastewater in a single process. A parametric study was performed to determine the optimum conditions. The results showed that reaction temperature and theoretical air percentage were the most effective parameters. Sugar derivatives were almost completely destroyed at the optimum conditions and total organic carbon (TOC) and chemical oxygen demand (COD) removals were determined as 91% and 87%, respectively, indicating a high mineralization degree, which was the main goal of advanced oxidation. The reaction kinetics were investigated by pseudo‐homogeneous and heterogeneous models based on two different parameters: sucrose and TOC concentration. The degree of fit showed that the reaction order was determined as two for the pseudo‐homogeneous approach. According to the surface concentration calculations for heterogeneous models, the presence of mass transfer limitations was only observed for oxygen as gas reactant. All heterogeneous models also fitted the reaction rate data accurately, but the Mars–van Krevelen was the selected model for sucrose and TOC oxidation with the best fit.

Magnetite Nanoparticles as Solar Photo-Fenton Catalysts for the Degradation of the 5-Fluorouracil Cytostatic Drug.

Heterogeneous catalysts based on magnetite nanoparticles, Fe3O4, were prepared by the chemical coprecipitation method using iron (III) chloride as a salt precursor. The physicochemical properties of the nanoparticles were determined by different techniques and the efficiency was evaluated for the degradation of the cytostatic drug, 5-fluorouracil (5-FU), in aqueous solution by photo-Fenton process under simulated solar radiation. The most influential parameters, namely pH of the solution, catalyst load, H2O2 dosage, and use of radiation, were studied and optimized in the degradation process. The optimal conditions to achieve a 100% degradation of 5-FU (10 mg L-1) and a high mineralization degree (76%) were established at the acidic pH of 3.0, 100 mg L-1 of catalyst loading, and 58 mM of H2O2 under simulated solar radiation. The contribution of iron leaching to the catalyst deactivation, the role of the dissolved iron ions on homogenous reactions, and the stability of the catalyst were assessed during consecutive reaction cycles.

Degradation of the Selected Antibiotic in an Aqueous Solution by the Fenton Process: Kinetics, Products and Ecotoxicity.

Sulfonamides used in veterinary medicine can be degraded via the Fenton processes. In the premise, the process should also remove the antimicrobial activity of wastewater containing antibiotics. The kinetics of sulfathiazole degradation and identification of the degradation products were investigated in the experiments. In addition, their toxicity against Vibrio fischeri, the MARA® assay, and unselected microorganisms from a wastewater treatment plant and the river was evaluated. It was found that in the Fenton process, the sulfathiazole degradation was described by the following kinetic equation: r0 = k CSTZ-1 or 0 CFe(II)3 CH2O20 or 1 CTOC-2, where r0 is the initial reaction rate, k is the reaction rate constant, C is the concentration of sulfathiazole, Fe(II) ions, hydrogen peroxide and total organic carbon, respectively. The reaction efficiency and the useful pH range (up to pH 5) could be increased by UVa irradiation of the reaction mixture. Eighteen organic degradation products of sulfathiazole were detected and identified, and a possible degradation mechanism was proposed. An increase in the H2O2 dose, to obtain a high degree of mineralization of sulfonamide, resulted in an increase in the ecotoxicity of the post-reaction mixture.

Assessment of soil-gas radon concentration over lithologies: a case study from district Karak, Khyber Pakhtunkhwa, Pakistan.

The current study is aimed to determine the variation of soil-gas radon concentrations over different rock formations representing diverse lithologies in the district of Karak, Khyber Pakhtunkhwa, Pakistan. The stratigraphic units were grouped on the basis of lithological contents into four categories, i.e., limestone, evaporites, claystone/mudstone, and sandstone. The highest average soil-gas 222Rn concentration (544Bq/L) was found in the uranium-bearing Dhok Pathan Formation of the Pliocene age, while the lowest radon levels (0.15Bq/L) were observed in the salt-bearing strata of Bahadurkhel Salt of Eocene age showing the non-uraniferous nature of the salt. High radon potential associated with the Dhok Pathan Formation is likely to be related to the high degree of uranium mineralization which is contributing to the elevated soil-gas radon levels. The study revealed that the soil-gas radon concentration in all lithologies is varying in the order of RnSandstone > RnLimestone > RnClaystone/Mudstone > RnEvaporites with the highest radon levels in the sandstone unit of uranium-bearing Dhok Pathan Formation. High fluctuations of soil-gas radon levels observed in this study evidently show that lithology and uranium mineralization have strong control over the 222Rn concentrations.

Photocatalytic activity of graphene oxide-TiO2 nanocomposite on dichlorvos and malathion and assessment of toxicity changes due to photodegradation

Heterogeneous photocatalysis was used for the removal of two widely used organophosphorus pesticides, dichlorvos, and malathion from water. Graphene oxide-TiO2 nanocomposite (GOT) was synthesized and used as a photocatalyst for the removal of these pesticides. Batch studies for optimizing photocatalytic degradation and mineralization of pesticides over 80 min were conducted by varying the pH (2–10), catalyst dose (20 mg/L-200 mg/L), and initial pesticide concentration (0.5 mg/L-20 mg/L), and the irradiation source (125 W UV and visible lamp). Degradation kinetics for the pesticides were evaluated. Ellman assay was used to estimate the toxic effect of pesticides and evaluate toxicity reduction due to treatment. The highest degradation and mineralization of dichlorvos and malathion was observed at pH 6 and the optimum catalyst dose was 60 mg/L. Under UV irradiation, 80% and 90% degradation were observed for dichlorvos and malathion, respectively for 0.5 mg/L initial pesticide concentration. The photocatalytic degradation reaction followed Langmuir-Hinshelwood kinetics. A high degree of mineralization was achieved for both the pesticides. Analysis of the results revealed that the residual toxic effect after photocatalysis was primarily due to the residual parent compound. A comparative study revealed that GOT yielded better pesticide degradation compared to commercially available TiO2 under both UV and visible irradiation.

Study and Application of Ultrafine Temperature-Resistant and Salt-Tolerant Swellable Particles in Low Permeability Reservoirs

Based on the characteristics of low-permeability oil and gas reservoirs and the requirements for profile control and water plugging and for water cut decrease and production increase in the high water cut stage of the middle and late exploitation periods, ultrafine temperature-resistant and salt-tolerant swellable particles DS-1 suitable for low permeability oilfields were prepared by introducing N,N-dimethylacrylamide(DMAA) monomers into the 2-acrylamido-2-methylpropanesulfonic acid (AMPS)/acrylamide(AM)/N,N-dimethylbisacrylamide ternary crosslinking system. The median of initial particle size was 22.00 μm, and is compatible with formation pore throats. A static water absorption experiment showed that the particles can still maintain a high swelling ratio after 15 days at a high temperature and high mineralization degree, so they have long-term stability. The physical and chemical properties of the particles were analyzed microscopically using the infrared spectrum method and the scanning electron microscope (SEM) method. A dynamic displacement experiment confirmed that the particles can effectively plug dominant channels of waterflooding, increase the injection pressure, and improve the interlayer and intralayer heterogeneity. In the field experiment, the swellable particles DS-1 were used as a main slug for water plugging operations, and a good water cut decrease and oil production increase effect was obtained.

Reuse of wool dyeing wastewater after electrochemical treatment at a BDD anode

The present study aimed to evaluate the feasibility of reusing dyeing wastewaters, treated by electrochemical oxidation (EO) with a boron-doped diamond anode, in new dyeing processes. A wool fabric was dyed with acid dye Telon® Blue RR, using Avolan® UL 75 and sodium sulfate as dyeing auxiliaries, and the wastewater obtained was treated by EO at different applied current densities and treatment times. The treated wastewater was then reused in the dyeing process, being the resulting wastewater submitted to a new EO treatment and a posterior reuse in another dyeing cycle. The successive dyeing processes were evaluated in terms of dye-uptake, colour difference (ΔE*), and colour fastness to washing. In all EO treatments, before and after the reuse, complete discolouration of the effluents was observed, alongside with partial organic compounds mineralization. For all the applied experimental conditions, salt content was recovered in full, eliminating the need of salt addition in the reused dyeing baths. The dyeing processes performed with treated wastewater presented increased dye-uptakes, with consequent darker colour of the dyed fabrics, suggesting that the amount of dye in the reuse dyeing baths could be reduced. Moreover, higher affinity between the dye and the wool fabric was observed when using treated wastewaters with lower organic load and higher mineralization degree. For these wastewater conditions, obtained at the highest applied current density and treatment time studied, a reduction of 15 % in dye concentration resulted in a ΔE* of 1.19, complying with the less restrictive ΔE* requirements.

Efficient activation of peroxymonosulfate mediated by Co(II)-CeO2 as a novel heterogeneous catalyst for the degradation of refractory organic contaminants: Degradation pathway, mechanism and toxicity assessment

A series of Co(II)-CeO2 mixed metal oxides were synthesized by a facile hydrothermal-calcination procedure for activating peroxymonosulfate (PMS) and degrading toxic and difficult biodegradable organics. Co(II)-CeO2 showed excellent degradation performance toward rhodamine B (RhB), toluidine blue, methylene blue and diclofenac. RhB is a refractory organic contaminant, and ecotoxicological evaluation unraveled its harmfulness to the biosphere. RhB was selected as the model pollutant to investigate catalytic mechanisms. Parameters affecting degradation performance were profoundly investigated, including Co:Ce feed ratio, initial pH, PMS dosage, catalyst dosage, RhB concentration, coexisting ions and reaction temperature. Reaction mechanisms were proposed based on density functional theory calculations and identifications of reactive oxygen species. Improvements have been achieved in seven aspects compared to previous studies, including 100% degradation ratio in both real water samples and each reuse of the catalyst, ultrafast degradation rate, cost-effectiveness of the catalyst, toxicity-attenuation provided by the developed degradation method, high degree of mineralization for the model pollutant, negligible leaching of active sites, and the enhancement of catalytic performance by utilizing trace leached cobalt, endowing the technique with broad applicability and prospect.