Effect Of pH Research Articles

Separation of ovomucin from duck egg white and its “acid-tight /alkali-loose” self-supporting gel properties under different pH

Ovomucin is a key component in maintaining the viscous nature of egg white and has vast potential in the utilization of food industry. The objectives of the study were to determine the effect of different pH on the extractability and gel properties of ovomucin. After removing lysozyme through ion exchange, the diluted duck egg white was acidified to a narrow pH range (4.50, 4.75, 5.00, 5.25, 5.50, 5.75 and 6.00) to precipitate ovomucin. By comprehensive study of purity, yield, and convenience of large-scale preparation, 4.75 was chosen as the optimal pH to extract ovomucin with the highest purity of 85.17 ± 2.31% and a compromised yield of 4.60 ± 0.06 mg/g duck egg white. A series of self-supporting gels were prepared with freeze-dried ovomucin powder at room temperature upon rehydration and centrifugation, and the gels properties were highly associated with pH. Gel formed around pH 5 was the aggregate of natural globular proteins with lowest hydrophobicity and electrostatic interaction, relatively dense structure and high water-holding capacity (WHC). Stronger acidic conditions disrupted the disulfide bonds and formed a rougher spherical aggregate. Under alkaline conditions, however, the protein gradually unfolded and broke into linear basic polypeptides, thus a porous three-dimensional network was formed. Overall, this study provided insights into the formation mechanism of the “acid-tight/alkali-loose” ovomucin gels, and introduced a potential candidate for the development of bioactive substance delivery materials.

Development of Response Surface Approach for Determination of Paracetamol, Chlorpheniramine Maleate, Caffeine and Ascorbic Acid by Green HPLC Method: A Desirability-Based Optimization.

Design of experiment is an efficient and cost-effective tool to optimize the chromatographic separation of a multicomponent mixture. The central composite design was conducted to develop and optimize a green high performance liquid chromatography (HPLC) method for simultaneous quantitation of a quaternary mixture of paracetamol, chlorpheniramine maleate, caffeine and ascorbic acid in their pharmaceutical dosage form as well as the determination of their dissolution profile. A five-level three-factor model was performed to investigate the effect of mobile phase composition, pH and flow rate on enhanced resolution and short run time. Analysis was performed using a Kinitex EVO C18 column and a mobile phase composed of methanol: 0.02M phosphate buffer pH3.3 (34:66, v/v) at 1.0mL/min using photodiode array detection. Optimum chromatographic separation was achieved in <6min with a desirability of 0.999. Linearity was achieved over a range of 1.00-300.00, 1.00-50.00, 2.00-50.00 and 2.00-100.00μg/mL for paracetamol, chlorpheniramine maleate, caffeine and ascorbic acid, respectively, with a limit of detection (<0.1μg/mL). The greenness profile was evaluated using the analytical eco-scale and Analytical GREEnness Metric Approach with values of 81 and 0.77, respectively.

High-resolution carbon and oxygen isotopic compositions of cultured brachiopods: Effect of pH, temperature and growth

Brachiopod shells are ubiquitous since the Early Cambrian up to now. As they secrete a shell made of low-magnesium calcite, more resistant to diagenesis than biocarbonates richer in Mg, their geochemical signatures are generally considered a powerful tool for paleo-environmental and paleo-climatic reconstructions. However, gaps in knowledge still remain on the underlying controls of the shell chemistry, in particular at a high spatial resolution. In this study, in situ oxygen and carbon isotope measurements by SIMS (Secondary Ion Mass Spectrometry) were performed in brachiopod shells of the cold-temperate water species Magellania venosa, constituted of a primary and a secondary layer. The individual specimens studied here grew under controlled conditions mimicking the natural environment and in experiments under low-pH (high pCO2) and high-temperature conditions. Transversal carbon and oxygen profiles showed a “brachiopod pattern” typical of extant two-layered brachiopods, with the primary layer depleted in 18O and 13C relative to equilibrium and the secondary layer showing a gradual increasing trend until reaching a near-equilibrium plateau. Overall, shells cultured at low pH were found to have δ18O and δ13C values closer to equilibrium when compared to shells from the control experiment. These near-equilibrium values may reflect a decrease in shell precipitation rate, leading to less kinetic effects, and/or a more rapid kinetics for the equilibration between DIC species and water. By close pairing of seawater δ18O and δ13C to that of shell microstructure, our study enables us to derive layer-specific C and O enrichment factors, which show the extent of pH and temperature effects superimposed on the seawater δ18O and DIC δ13C signal inherited. Finally, we show that during brachiopod shell growth, newly precipitated calcite is added to the calcite already existing, thus empirically validating the conceptual accretionary growth model proposed by Ackerly (1989).

Exploring highly electro-active zinc peroxide nanorod for selective detection of hydrazine

Hydrazine (N2H4), widely used as a raw material for producing synthetic catalysts, agricultural chemicals, and pharmaceutical products, has had an irreversible impact on air, water, and soil in the environment because of its high toxicity. To prevent making it lethal contamination should be monitored and detected. Here in this work, for the first time, Zinc peroxide (ZnO2) nanorods (NRs) were synthesized using a simple hydrothermal method to modify the gold electrode (AuE) for the fabrication of the ZnO2@AuE sensor. The fabricated sensor was successfully applied for the selective and efficient detection of hydrazine based on the chronoamperometry technique. According to theoretical calculations, the metal peroxide nanorods result in high oxygen vacancies, surface defects, and Zn ratios. This triggers substantial electron transfer, effectively enhancing the conductivity, electrocatalytic, and stability properties of the AuE with economic benefits. The effect of surface modification on the bare electrode was analyzed using the EIS technique. The ZnO2/Au electrode's electrochemical behavior towards hydrazine was studied using cyclic voltammetry (CV) at a scan rate of 70 mVs−1. Further, chronoamperometry was applied to investigate the effect of time, pH, nanorod concentration, and scan rate on the analytical performance parameters of the electrode ZnO2@AuE. The developed sensor (ZnO2/AuE) demonstrated an excellent detection limit (LOD) of 4.09 nM and good sensitivity of 2.4 × 10−2 µAµM−1cm−2 towards the oxidation of hydrazine having a fast response time (within 5 s). The developed sensors promise reproducible results along with good stability, which makes them effective for the electrochemical sensing of hydrazine. Such outstanding sensing performance is attributed to the tailored direct electrochemical redox surface of ZnO2, which led to selective sensing of hydrazine in tap, distilled, and sewage water. Keeping these features into consideration, our developed sensor can be adopted for real applications, especially for environmental surveillance.

Adsorption of the Antibiotic Roxithromycin on Low-Cost Food Waste Materials: Batch and Column Studies

Antibiotics are widely utilized for a variety of medical conditions. Antibiotic residues in wastewater are dangerous to all living beings. Antibiotics remain in the wastewater environment when general treatment plant technologies are employed. The literature has numerous techniques for getting rid of antibiotics. Compared to other techniques for removing contaminants in the solution environment, the adsorption method is preferred due to its benefits, such as ease of use, high efficiency, and low cost. The study investigated using the green walnut shell (GWS), a natural sorbent, as an adsorbent to discharge roxithromycin (ROX) antibiotics from the solution medium. Adsorption conditions were studied in batch and continuous systems. pH, adsorbent amount, interaction time, sorbate concentration, and salt effect parameters were investigated in the batch system. The data obtained were calculated with kinetic and isotherm models. The adsorption process has been based on the so-called pseudo-second-order kinetic model. GWS was characterized using SEM and FTIR techniques. The amount of absorbent, flow rate, and breakdown in the continuous system were explored. In the batch system, the adsorption equilibrium was set up at the solution's original pH with 0.1 g of adsorbent in 40 minutes, and 78% ROX removal was achieved. The optimum flow rate and adsorbent amount in the continuous system were determined as 0.1 mL/min and 0.3 g, respectively.

A green and economic approach to synthesize magnetic Lagenaria siceraria biochar (γ-Fe2O3-LSB) for methylene blue removal from aqueous solution.

In the printing and textile industries, methylene blue (a cationic azo dye) is commonly used. MB is a well-known carcinogen, and another major issue is its high content in industrial discharge. There are numerous removal methodologies that have been employed to remove it from industrial discharge; however, these current modalities have one or more limitations. In this research, a novel magnetized biochar (γ-Fe2O3-LSB) was synthesized using Lagenaria siceraria peels which were further magnetized via the co-precipitation method. The synthesized γ-Fe2O3-LSB was characterized using FTIR, X-ray diffraction, Raman, SEM-EDX, BET, and vibrating sample magnetometry (VSM) for the analysis of magnetic properties. γ-Fe2O3-LSB showed a reversible type IV isotherm, which is a primary characteristic of mesoporous materials. γ-Fe2O3-LSB had a specific surface area (SBET = 135.30 m2/g) which is greater than that of LSB (SBET = 11.54 m2/g). γ-Fe2O3-LSB exhibits a saturation magnetization value (Ms) of 3.72emu/g which shows its superparamagnetic nature. The batch adsorption process was performed to analyze the adsorptive removal of MB dye using γ-Fe2O3-LSB. The adsorption efficiency of γ-Fe2O3-LSB for MB was analyzed by varying parameters like the initial concentration of adsorbate (MB), γ-Fe2O3-LSB dose, pH effect, contact time, and temperature. Adsorption isotherm, kinetic, and thermodynamics were also studied after optimizing the protocol. The non-linear Langmuir model fitted the best to explain the adsorption isotherm mechanism and resulting adsorption capacity ( =54.55mg/g). The thermodynamics study showed the spontaneous and endothermic nature, and pseudo-second-order rate kinetics was followed during the adsorption process. Regeneration study showed that γ-Fe2O3-LSB can be used up to four cycles. In laboratory setup, the cost of γ-Fe2O3-LSB synthesis comes out to be 162.75 INR/kg which is low as compared to commercially available adsorbents. The results obtained suggest that magnetic Lagenaria siceraria biochar, which is economical and efficient, can be used as a potential biochar material for industrial applications in the treatment of wastewater.

Glyphosate-environmental variables interaction: How does it affect the parasite Chordodes nobilii?

The worldwide used herbicide Glyphosate can interact with environmental variables, but there is limited information on the influence of environmental stressors on its toxicity. Environmental changes could modify glyphosate effects on non-target organisms, including parasites such as gordiids. The freshwater microscopic larvae of the gordiid Chordodes nobilii are sensitive to several pollutants and environmental variables, but their combined effect has not been evaluated yet. The aim of this study was to evaluate the impact of temperature, pH and exposure time on the toxicity of Glyphosate to C. nobilii larvae. A protocol was followed to evaluate the infectivity of larvae treated with factorial combinations of concentration (0 and 0.067 mg/L), exposure time (24 and 48 h), temperature (18, 23 and 28 °C), and pH (7, 8 and 9). The reference values were 23 °C, pH 8 and 48 h. The interaction effect on the infectivity of gordiid larvae was assessed post-exposure using Aedes aegyptii larvae as host. Results were evaluated using GLMM, which does not require data transformation. The modeling results revealed three highly significant triple interactions. Glyphosate toxicity varied depending on the combination of variables, with a decrease being observed after 24 h-exposure at pH 7 and 23 °C. Glyphosate and 28 °C combination led to slightly reduced infectivity compared to temperature alone. This study is the first to report the combined effects of glyphosate, temperature, pH and time on a freshwater animal. It demonstrates that a specific combination of factors determines the effect of glyphosate on a non-target organism. The potential use of C. nobilli as a bioindicator is discussed. In the context of global warming and considering that the behavioral manipulation of terrestrial hosts by gordiids can shape community structure and the energy flow through food webs, our results raise concerns about possible negative effects of climate change on host-parasite dynamics.

Abiotic Ribose Synthesis Under Aqueous Environments with Various Chemical Conditions.

Ribose is the defining sugar in ribonucleic acid (RNA), which is often proposed to have carried the genetic information and catalyzed the biological reactions of the first life on Earth. Thus, abiological processes that yield ribose under prebiotic conditions have been studied for decades. However, aqueous environments required for the formation of ribose from materials available in quantity under geologically reasonable models, where the ribose formed is not immediately destroyed, remain unclear. This is due in large part to the challenge of analysis of carbohydrates formed under a wide range of aqueous conditions. Thus, the formation of ribose on prebiotic Earth has sometimes been questioned. We investigated the quantitative effects of pH, temperature, cation, and the concentrations of formaldehyde and glycolaldehyde on the synthesis of diverse sugars, including ribose. The results suggest a range of conditions that produce ribose and that ribose could have formed in constrained aquifers on prebiotic Earth.

Adsorption performance and mechanism of Arsenic(III) and Arsenic(V) by using copper-manganese binary oxide

ABSTRACT Arsenic contamination threatens the safety of drinking water in many areas of the world. As(V) is less toxic and easier to remove than As(III). Hence, it is essential to oxidise As(III) to As(V). Based on the previous studies, Cu-Mn binary oxide (CMBO) (with a molar ratio of Cu/Mn = 3:1) was prepared by a two-step method. The results showed that CMBO has a large specific surface area (67.74 m2/g) and pore size (16.87 nm). Moreover, CMBO has an inconspicuous crystal structure and abundant hydroxyl groups, which are favourable for arsenic adsorption. The adsorption kinetics results indicated that As(III) was oxidised to As(V) during the adsorption process, and the adsorption rate for As(V) removal was faster than that for As(III) removal. The saturated adsorption capacities of As(III) and As(V) were calculated to be 64.17 mg/g and 84.87 mg/g via the Langmuir isotherm model, respectively. The results of the pH effect studies indicated that acidic conditions promoted the removal of both As(III) and As(V) by CMBO due to the electrostatic attraction. The spectroscopic analysis results demonstrated that Mn oxides within CMBO played a vital role in As(III) oxidation. The removal of As(III) by CMBO was attributed to the synergistic effect of As(III) oxidation by Mn oxides and As sorption by Cu oxides. Overall, CMBO is a promising sorbent with great potential for removing arsenic.

Heteroaggregation Kinetics of Nanoplastics and Soot Nanoparticles in Aquatic Environments

Heteroaggregation between polystyrene nanoplastics (PSNPs) and soot nanoparticles (STNPs) in aquatic environments may affect their fate and transport. This study investigated the effects of particle concentration ratio, electrolytes, pH, and humic acid on their heteroaggregation kinetics. The critical coagulation concentration (CCC) ranked CCCPSNPs > CCCPSNPs-STNPs > CCCSTNPs, indicating that heteroaggregation rates fell between homoaggregation rates. In NaCl solution, as the PSNPs/STNPs ratio decreased from 9/1 to 3/7, heteroaggregation rate decreased and CCCPSNPs-STNPs increased from 200 to 220mM due to enhanced electrostatic repulsion. Outlier was observed at PSNPs/STNPs=1/9, where CCCPSNPs-STNPs=170mM and homoaggregation of STNPs dominated. However, in CaCl2 solution where calcium bridged with STNPs, heteroaggregation rate increased and CCCPSNPs-STNPs decreased from 26 to 5mM as the PSNPs/STNPs ratio decreasing from 9/1 to 1/9. In composite water samples, heteroaggregation occurred only at estuarine and marine salinities. Acidic condition promoted heteroaggregation via charge screening. Humic acid retarded or promoted heteroaggregation in NaCl or CaCl2 solutions by steric hindrance or calcium bridging, respectively. Other than van der Waals attraction and electrostatic repulsion, heteroaggregation was affected by steric hindrance, hydrophobic interactions, π−π interactions, and calcium bridging. The results highlight the role of black carbon on colloidal stability of PSNPs in aquatic environments. Environmental ImplicationsNanoplastics (NPs) as emerging contaminants in aquatic environments may encounter soot nanoparticles (STNPs), which are refractory and hazardous black carbon. Their heteroaggregation may affect their environmental fate, transport, and risks.This study investigated the effects of particle concentration ratio, electrolytes, pH, and humic acid on heteroaggregation kinetics of polystyrene NPs (PSNPs) and STNPs under environmental aqueous conditions. Results demonstrated that STNPs destabilized PSNPs via heteroaggregation and modified their physicochemical properties including size and surface charge. Humic acid and electrolytes may stabilize them in freshwater, but could induce heteroaggregation in estuary and ocean to cause contaminant accumulation in these benthic environments.

Microbial production of 3-hydroxypropionic acid by acetic acid bacteria: modeling including the buffering capacity of the biological medium enables prediction of pH and metabolite concentrations

A mathematical model of the fed-batch bioconversion of 1,3-propanediol into 3-hydroxypropionic acid using acetic acid bacteria is proposed. The model includes the microbial growth, the oxidation of 1,3-propanediol to 3-hydroxypropionaldehyde followed by a second oxidation reaction to 3-hydroxypropionic acid. The inhibitory effect of the total acid concentration upon the biological reactions was considered as well as the effect of pH on bacterial growth. A special attention was paid to make accurate pH predictions as pH is a key parameter that influences the microbial growth and bioconversion and also defines the strategy of downstream processing for acid recovery. The buffering capacity of the complex biological medium was found to change throughout the bioconversion. In addition to describing satisfactorily a set of experiments reported in the literature, the model was successfully used to predict metabolite concentrations and the resulting pH in new operating conditions with free pH dynamics. A sensitivity analysis was performed to identify the most influential parameters of the model. The proposed model represents a valuable tool for bioprocess design as it describes the detailed kinetics of 1,3-propanediol oxidation to 3-hydroxypropionic acid by acetic acid bacteria in bioreactor. Additionally, the pH prediction is a major feature of this model, which could guide the identification of optimal operating conditions for microbial activity with a simultaneous in-situ recovery process.

Peptides-modified cellulose microspheres for adsorption of ochratoxin A: Performance and mechanism

In this study, peptides with ochratoxin A (OTA) recognition and adsorption capability were designed, among which lysine, histidine, arginine and tyrosine were crucial. Peptide CYFRFYSNLHPK showed the strongest affinity for OTA (Ka = 1.74 × 105 M−1). Theoretical calculations revealed that the differences in the affinity of peptides for OTA were attributed to differences in the type, number and position of amino acids residues. Peptides were conjugated with porous cellulose microspheres to form peptide-modified pretreatment materials (Pep-MPA-RCMs) for adsorption of OTA. The morphology and composition of the prepared Pep-MPA-RCMs were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction. The effects of pH, adsorption time, initial concentration and temperature on the adsorption process were investigated. The adsorption performance was correlated with the pseudo-second order kinetic and Sips adsorption isotherm model. Thermodynamic studies further proved that the adsorption was exothermic and the prepared Pep-MPA-RCMs showed the maximum adsorption capacity of 9.87 mg/g for OTA at 25℃. A simple adsorption column for OTA was prepared by using Pep-MPA-RCMs as filler material, which still maintained more than 80 % of the removal rate after five consecutive adsorption-elution cycles. The prepared pretreatment material was successfully applied to remove OTA in real samples and was a promising adsorbent for practical applications.

Improved Enzymatic Production of the Fucosylated Human Milk Oligosaccharide LNFP II with GH29B α-1,3/4-l-Fucosidases.

Five GH29B α-1,3/4-l-fucosidases (EC 3.2.1.111) were investigated for their ability to catalyze the formation of the human milk oligosaccharide lacto-N-fucopentaose II (LNFP II) from lacto-N-tetraose (LNT) and 3-fucosyllactose (3FL) via transglycosylation. We studied the effect of pH on transfucosylation and hydrolysis and explored the impact of specific mutations using molecular dynamics simulations. LNFP II yields of 91 and 65% were obtained for the wild-type SpGH29C and CpAfc2 enzymes, respectively, being the highest LNFP II transglycosylation yields reported to date. BbAfcB and BiAfcB are highly hydrolytic enzymes. The results indicate that the effects of pH and buffer systems are enzyme-dependent yet relevant to consider when designing transglycosylation reactions. Replacing Thr284 in BiAfcB with Val resulted in increased transglycosylation yields, while the opposite replacement of Val258 in SpGH29C and Val289 CpAfc2 with Thr decreased the transfucosylation, confirming a role of Thr and Val in controlling the flexibility of the acid/base loop in the enzymes, which in turn affects transglycosylation. The substitution of an Ala residue with His almost abolished secondary hydrolysis in CpAfc2 and BbAfcB. The results are directly applicable in the enhancement of transglycosylation and may have significant implications for manufacturing of LNFP II as a new infant formula ingredient.

Phosphorus immobilization/release behavior of lanthanum-modified bentonite amended sediment under the dual effects of pH and dissolved organic carbon

Phosphorus immobilization/release behavior of lanthanum-modified bentonite amended sediment under the dual effects of pH and dissolved organic carbon

Antimony isotopic fractionation induced by Sb(V) adsorption on β-MnO2

Antimony (Sb) isotopes hold immense promise for unraveling Sb biogeochemical cycling in environmental systems. Mn oxides help control the fate of Sb via adsorption reactions, yet the behavior and mechanisms of Sb isotopic fractionation on Mn oxides are poorly understood. In this study, we examine the Sb isotopic fractionation induced by adsorption on β-MnO2 in different experiments (kinetic, isothermal, effect of pH). We observe that adsorption on β-MnO2 surfaces preferentially enriches lighter Sb isotopes through equilibrium fractionation, with Δ123Sbaqueous-adsorbed of 0.55–0.79 ‰. Neither the pH or surface coverage affects the fractionation magnitude. The analysis of extended X-ray absorption fine structure (EXAFS) demonstrates that the enrichment of light isotope results from the adsorption of inner-sphere complexation on solids. Our finding of this study enhances our comprehension of the impact of β-MnO2 on Sb isotopic fractionation behavior and mechanism and facilitate the applicability of Sb isotopes as effective tracers to elucidate the origins and pathways of Sb contamination in environmental systems, as well as provide a new insight into forecasting the isotopic fractionation of other similar metals adsorbed by manganese oxides.

A novel combined method for nitrate removal by chemical Pd–Cu/alumina bimetallic catalyst and biohydrogen produced by Rhodobacter johrii VT1 in an anaerobic, photo-fermentation process

In this study, biohydrogen was produced by R. johrii strain VT1 using an anaerobic photo-fermentation process on low-cost industrial wastewater and then used for nitrate reduction in the presence of a chemical catalyst. The effect of substrate, light intensity, and pH on biohydrogen production was investigated. For efficient nitrate reduction, a Pd–Cu/alumina bimetallic catalyst was prepared and analyzed by XRD, FTIR, FESEM, and ICP. Accumulative biohydrogen production was 284.67 ml/h (0.409 ± 0.005 mol/m3h), with molasses, a light intensity of 5300 lux, and a pH of 9. Nitrate removal efficiency was 81.70%, and nitrogen selectivity was 94.25%. The XRD results also showed the stability of the catalyst structure during the reduction. Our study shows that this combined method is effective for nitrate removal and has the potential for large-scale work because of the affordable and sustainable green hydrogen production from wastewater. This is the first report of using biological hydrogen for harmful nitrate removal from drinking water in the presence of a chemical catalyst.

The effect of soil types, pH, and geographical locations on carcinogenic metal buildup in Oryza sativa cultivated in Ghana.

This study investigated the impact of soil type, pH, and geographical locations on the accumulation of arsenic (As), lead (Pb), and cadmium (Cd) in rice grains cultivated in Ghana. One hundred rice farms for the sampling of rice grains and soil were selected from two regions in Ghana-Volta and Oti. The concentrations of As, Pb, and Cd were analyzed using ICP-OES. Speciation modeling and multivariate statistics were employed to ascertain the relations among measured parameters. The results showed significant variations in soil-As, Pb, and Cd levels across different soil types and pH ranges, with the highest soil-As and Cd found in alkaline vertisols. For soil-As and Cd, the vertisols with a pH more than 7.0 exhibited the highest mean concentration of As (2.51 ± 0.932 mgkg-1) and Cd (1.00 ± 0.244 mgkg-1) whereas for soil-Pb, the luvisols of soil types with a pH less than 6.0 exhibited the highest mean concentration of Pb (4.91 ± 1.540 mgkg-1). Grain As, Pb, and Cd also varied across soil types and pH levels. In regards to grain-As, the vertisols soil type, with a pH less than 6.0, shows the highest mean concentration of grain As, at 0.238 ± 0.107 mgkg-1. Furthermore, vertisols soil types with a pH level less than 6.0 showed the highest mean concentration of grain Cd, averaging at 0.231 ± 0.068 mgkg-1 while luvisols, with a pH less than 6.0, exhibited the highest mean concentration of grain Pb at 0.713 ± 0.099 mgkg-1. Speciation modeling indicated increased bioavailability of grains Cd2+ and Pb2+ ions in acidic conditions. A significant interaction was found between soil-Cd and pH, affecting grain-As uptake. The average concentrations of soil As, Pb, and Cd aligned with international standards. Generally, the carcinogenic metals detected in grain samples collected from the Volta region are higher than that of the Oti region but the differences are insignificant, and this may be attributed to geographical differences and anthropogenic activities. About 51% of the study area showed a hazard risk associated with grain metal levels, although, no carcinogenic risks were recognized. This study highlights the complex soil-plant interactions governing metal bioaccumulation and emphasizes the need for tailored strategies to minimize metal transfer into grains.

Treatment of Water Contaminated by Ship Oil: Study of Adsorption in a Fixed-Bed Column

Aquatic macrophytes like Salvinia sp. have rapid proliferation and a great capacity for ecological adaptation. In addition to these characteristics, this study points to their ability to adsorb contaminants such as dyes, metals, and oils. This work aims, through an adsorption study, to propose an alternative treatment using chemically modified Salvinia sp. (SOH) biomass to remove oil from water. Batch adsorption experiments were performed to observe the effects of concentration, pH, time, temperature, desorption, and reuse of the biomass. The adsorption mechanisms, performance, kinetics, isotherm, thermodynamics, and reusability of biomass were evaluated. Both adsorbents were well-defined by the Freundlich model isotherm. According to the results obtained, the qmax was 898.0 mg g−1 for SOH in oil-in-salt water emulsion in 15 min and 930.59 mg g−1 for Salvinia sp. in natura (SS) in the oil-in-water emulsion. In the fixed-bed column adsorption, the adsorption capacity was 2.99 g g−1 for SS and 3.49 g g−1 for SOH, and the saturation capacity was 42.89 g g−1 SS and 42.99 g g−1 SOH. According to the adsorption models, the Bohart–Adams model best fits the experimental data of this study. The SOH adsorbed oil recovery test was successful, with 100% oil recovery.

KMnO4 modified magnetic hydrochar for efficient adsorption of malachite green and methylene blue from the aquatic environment

This study exploited magnetic citrus peel hydrochar (MHC) modified by KMnO4 (MHC/Mn) for the removal of methylene blue (MB) and malachite green (MG). Effects of initial concentration, pH, dosage, temperature, and ion strength on MHC/Mn adsorption properties were investigated. The adsorption kinetics, isotherm, and mechanism were further explored. The results indicated that Fe3O4 was successfully embedded and MnO2 was coated on MHC after modification. The experiment data were well fitted to the pseudo-second-order kinetic model and Langmuir isotherm model. Thermodynamic parameters showed that the adsorption of MHC/Mn to MB is spontaneous and endothermic, and the adsorption of MG is spontaneous and exothermic. The mechanism of MB and MG interaction with MHC/Mn includes electrostatic interaction, hydrogen bond, surface complexation, and π-π interaction. The maximum adsorption capacity of MB and MG calculated were 175.63 mg/g and 1402.17 mg/g. After four adsorption–desorption cycles, the removal rate of MB and MG were 85.11 % and 69.29 %. MHC/Mn is an economical and environmentally favorable adsorbent for the removal of MB and MG in wastewater.

Efficiency of dry drinking water treatment sludge as adsorbent for methylene blue and acid red 97 removal from aqueous solutions

In this study, drinking water treatment sludge (DWTS) was applied after drying as adsorbent for the removal of methylene blue (MB) and acid red 97 (AR97) from aqueous solutions. DWTS powder was characterized by X-ray fluorescence, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) methods. The thermal behavior of DWTS was examined and leaching tests were carried out to study its chemical stability. DWTS is mainly composed of aluminum (24.65%) and silicium (6.157%) and it has a mesoporous structure with a surface area of 92 m2.g-1. Batch adsorption experiments of MB and AR97 were achieved taking into account the effect of pH, initial dye concentration, adsorbent mass, contact time and temperature. The pseudo-second-order kinetic model provided the best correlation for both dyes, and the intra-particle diffusion is not the only rate-limiting step during the adsorption. Furthermore, the adsorption of MB and AR97 followed the Langmuir isotherm model with a maximum adsorption capacity equal to 46.30mg.g-1 and 135.13mg.g-1, respectively. Thermodynamically, the negative values of ΔG° for both the dyes assumes that the adsorption is favored and spontaneous and that the reaction is endothermic (ΔH°>0) and exothermic (ΔH°<0) for MB and AR97, respectively. The entropy ΔS° is positive and proves that there is randomness at the liquid/solid interface during the adsorption process. The results also exhibited that the adsorption of both dyes is a physical process. Finally, DWTS can be considered an effective and low-cost adsorbent due to its simple physical conditioning requiring only dewatering and grinding.