Continuous removal of pharmaceutical drug chloroquine and Safranin-O dye from water using agar-graphene oxide hydrogel: Selective adsorption in batch and fixed-bed experiments.

In this work, Chloroquine diphosphate, and the cationic dye Safranin-O were selectively removed from water using the agar-graphene oxide (A-GO) hydrogel, produced via simple one-step jellification process. The morphology of the A-GO biocomposite was characterized and batch experiments were performed, with adsorption isotherms satisfactorily fitting (R2 > 0.98) Sips (Safranin-O) and Freundlich (Chloroquine) isotherms. Driving force models and Fick's diffusion equation were applied to the modeling of kinetic data, and a satisfactory fit was obtained. Selective adsorption carried out in batch indicated that competitive adsorption occurs when both components are mixed in water solution - the adsorptive capacities dropped ∼10 mg g-1 for each component, remaining 41 mg g-1 for safranin-O and 31 mg g-1 for chloroquine. Fixed-bed breakthrough curves obtained in an adsorption column showed adsorption capacities over 63 mg g-1 and 100 mg g-1 for chloroquine and safranin-O, respectively, also exhibiting outstanding regenerative potentials. Overall, the biocomposite produced using graphene oxide proved to be a viable and eco-friendly alternative to continuously remove both contaminants from water.

Moringa oleifera extract promotes apoptosis-like death in Toxoplasma gondii tachyzoites in vitro.

Toxoplasma gondii is the causative agent of toxoplasmosis, and an important problem of public health. The current treatment for toxoplasmosis is the combination of pyrimethamine and sulphadiazine, which do not act in the chronic phase of toxoplasmosis and have several side-effects. This study evaluated the anti-T. gondii activity and potential mechanism of Moringa oleifera seeds' aqueous extract in vitro. The concentration of M. oleifera extract in HeLa cells was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cell viability assays. The presence of T. gondii was assessed by quantitative polymerase chain reaction and toluidine blue staining. Pyrimethamine and sulphadiazine were used as drug controls. Modifications in T. gondii morphology and ultrastructure were observed by electron microscopy. In vitro, the M. oleifera extract had no toxic effect on HeLa cells at concentrations below 50 µg mL−1. Moringa oleifera extract inhibits T. gondii invasion and intracellular proliferation with similar results for sulphadiazine + pyrimethamine, and also shows cellular nitric oxide production at a concentration of 30 µg mL−1. Electron microscopy analyses indicated structural and ultrastructural modifications in tachyzoites after treatment. We also observed an increase in reactive oxygen species production and a loss of mitochondrial membrane integrity. Nile Red staining assays demonstrated a lipid accumulation. Annexin V­fluorescein isothiocyanate and propidium iodide staining demonstrated that the main action of M. oleifera extract in T. gondii tachyzoites was compatible with late apoptosis. In conclusion, M. oleifera extract has anti-T. gondii activity in vitro and might be a promising substance for the development of a new anti-T. gondii drug.

Application of Moringa oleifera Lam. fractionated proteins for inactivation of Escherichia coli from water.

Chemical products traditionally used in the disinfection of water bodies often pose human health risks. For this reason, studies on natural coagulants such as Moringa oleifera Lam. represent an alternative for the inactivation of pathogenic microorganisms, among which is Escherichia coli. This study evaluated the effect of different concentrations of coagulants obtained from Moringa seed extracts and their protein fractions in the inactivation of E. coli during the coagulation/flocculation process. The coagulants studied were the aqueous extract, saline extract and protein fractions albumin and globulin, highlighting that the protein fractions were more effective on inactivating E. coli. The protein fraction globulin at a concentration of 10.0 mg L-1 showed bactericidal effects against E. coli within 18 min, whereas the albumin showed a bacteriostatic effect within 48 min because it isolated colonies in the sediment sample.

Adsorption study of heavy metals in aqueous solutions aiming at the treatment of contaminated groundwater.

This study evaluates the application of the vegetal activated carbon (AC), vegetable AC impregnated with Ag and Cu (0.08% m/m) and cationic SupergelTM SGC650H resin for adsorption of Fe3+ and Pb2+ ions in closed and batch system. The best adsorption capacities were obtained by using the cationic resin SGC650H, pH 3, temperature of 30 °C and stirring speed of 100 rpm. Thus, the kinetic and equilibrium experiments, in mono- and bicomponent, were performed using SGC650H resin, wherein the kinetic models of pseudo-first and pseudo-second order presented a good fit to the kinetic data, for mono- and bicomponent, respectively. The Langmuir isotherm adequately represented the monocomponent equilibrium data, showing maximum adsorption capacities values of 7.18 and 4.00 meq g-1 for Fe3+ and Pb2+, respectively. An inhibitory effect between the metal species was verified by fitting the modified extended Langmuir isotherm model to the binary equilibrium data, which allowed to predict changes in the surface affinity to the adsorbent by the metal ions. Based on the observed results, the use of SGC650H resin presents great potential for water treatment systems contaminated with heavy metals.

Groundwater quality monitoring of the Serra Geral aquifer in Toledo, Brazil.

In this work, a physical-chemical, elemental and microbiological groundwater monitoring was performed on wells of the Serra Geral aquifer, located in the western region of the Brazilian state of Paraná, along with an evaluation of the elemental composition of soil sediments in the region of groundwater monitoring. The monitoring was carried out in 10 wells distributed throughout the rural area of the municipality of Toledo-PR. Elemental analyses were performed using the analytical technique of total reflection X-ray fluorescence spectrometry. From the results obtained, it was observed that in some wells, iron and lead concentrations were above the maximum limits allowed by the Brazilian legislation in some months, demonstrating that the evaluated groundwater is susceptible to contamination. By the analysis of the soil sediments, the presence of iron and lead in the region soil/rock was verified, which may be associated to rainwater percolation making it necessary to periodically monitor the groundwater consumed by the population of the municipality of Toledo-PR.

Assessment of quinoxyfen phototransformation pathways by liquid chromatography coupled to accurate mass spectrometry.

Quinoxyfen has been recently identified as a priority hazardous substance in the field of the European water policy. In this work, its fate in aqueous samples and solid supports under UV and solar radiation is investigated. Diverse degradation experiments were carried out, at lab scale, using spiked aliquots of different aqueous matrices (ultrapure, treated wastewater and river water) irradiated at different wavelengths (λ = 254 nm, λ = 365 nm and solar light). Half-lives of quinoxyfen (2-26 min) depended on the wavelength and the intensity of radiation whilst the nature of the aqueous matrix did not play an important role in degradation kinetics. Moreover, experiments under solar radiation of doped silicone tubes were performed to simulate degradation when quinoxyfen is adsorbed on plant leaves or soil. As the compound is not completely mineralized, the identification of quinoxyfen transformation products (TPs) was performed by liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) injection of different irradiated time aliquots. The full-fragment ion spectra, at different collision energies, allowed the elucidation of the chemical structure of TPs formed by hydroxylation, cyclization or cleavage reactions. Five out of seven identified TPs have not been reported previously. The ecotoxicity simulation by software (TEST and ECOSAR) for TPs revealed that some of them could cause harmful effects to organisms such as Daphnia magna or Fathead minnow in a similar extent to the precursor; moreover, the time course profiles of major TPs (TP1 and TP2) revealed a much higher resistance to further photodegradation than quinoxyfen. Graphical abstract Quinoxyfen phototransformation pathways.

Biodegradability and toxicity assessment of a real textile wastewater effluent treated by an optimized electrocoagulation process.

In this work, the application of an iron electrode-based electrocoagulation (EC) process on the treatment of a real textile wastewater (RTW) was investigated. In order to perform an efficient integration of the EC process with a biological oxidation one, an enhancement in the biodegradability and low toxicity of final compounds was sought. Optimal values of EC reactor operation parameters (pH, current density and electrolysis time) were achieved by applying a full factorial 3(3) experimental design. Biodegradability and toxicity assays were performed on treated RTW samples obtained at the optimal values of: pH of the solution (7.0), current density (142.9 A m(-2)) and different electrolysis times. As response variables for the biodegradability and toxicity assessment, the Zahn-Wellens test (Dt), the ratio values of dissolved organic carbon (DOC) relative to low-molecular-weight carboxylates anions (LMCA) and lethal concentration 50 (LC50) were used. According to the Dt, the DOC/LMCA ratio and LC50, an electrolysis time of 15 min along with the optimal values of pH and current density were suggested as suitable for a next stage of treatment based on a biological oxidation process.

Antioxidant and rheological properties of guava jam with added concentrated grape juice.

BACKGROUND: Guava jam enriched by the addition of concentrated grape juice in the proportion of 30% (w/w) (ENR) was studied for its antioxidant potential and rheological behavior. Total phenolics content, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH(•)) scavenging activity and ß-carotene-linoleic acid coupled oxidation assays were used to evaluate the antioxidant properties of the samples during storage for 90 days at room temperature (25°C). RESULTS: The ENR showed a total phenolic content of 11.09 g GAE kg(-1) of jam at production, more than two-fold the phenolic content presented by the standard formulation (STA). For the ENR formulation the antioxidant capacity increased in almost 20% (P ≤ 0.05) with time on the ß-carotene assay and decreased with time on the DPPH assay. The enriched guava jam exhibited a non-Newtonian shear-thinning behavior at temperatures ranging from 25 to 55°C, and, moreover, presented higher stability than the standard formulation when exposed to temperature variation. CONCLUSION: ENR constitutes an original food product with a notable antioxidant potential, even greater than the potential presented by the standard guava jam, worldwide appreciated delicacy.

Improvement of the coagulation/flocculation process using a combination of Moringa oleifera lam with anionic polymer in water treatment.

The objective of this study is to investigate the impacts of anionic polymer as a flocculant aid on the coagulation/flocculation performance with a saline solution of Moringa oleifera as a coagulant to provide larger flocs and decrease the time sedimentation. For the tests, raw water was used from Pirapó River Basin (Maringá, Paraná, Brazil). Optimization of coagulation/flocculation tests was initially performed in a jar-test with a dosage of M. oleifera Lam (crude extract--MO, oil-extracted with ethanol--MO (et) and hexane--MO (hex) 1% m/v) as the coagulant that ranged from 10 to 60 mg L(-1) and of the anionic polymer 0.1% as a flocculant aid with a dosage that ranged from 0 to 0.4 mg L(-1). The parameters analysed were colour, turbidity and compounds with absorption in UV254nm. In view of the statistical analysis results, MO (hex) with a dosage of 30 mg L(-1) was chosen as a coagulant for the next tests of coagulation/flocculation. When anionic polymer was used alone (0.0 mg L(-1) of MO (hex)), parameters were not removed and there was no generation of heavy flocs as compared with the combination of MO (hex) with the anionic polymer. Statistical analysis showed that MO (hex) obtained the highest removals of the parameters analysed in lower dosages and no significant increase in parameters removal was observed when the polymer dosage was increased. The efficacy of the coagulant +/- anionic polymer was optimal when 30mg L(-1) of MO (hex) was used as a coagulant and 0.1 mg L(-1) of the anionic polymer was used as a flocculant aid, decreasing the time sedimentation from 1 h to 15 min.

Photocatalyst of manganese ferrite and reduced graphene oxide supported on activated carbon from cow bone for wastewater treatment.

The present research aimed to evaluate the photocatalytic activity of manganese ferrite (M) and reduced graphene oxide (G) supported on pulverized activated carbon from cow bone waste (PAC-MG). PAC-MG was characterized by different instrumental techniques. The efficiency of PAC-MG was evaluated using solar irradiation under different conditions of photocatalyst concentration, H2O2 concentration, and pH ranges for the discoloration of methylene blue dye (MB). The synergy between the nanomaterials potentiated the photocatalytic activity, reaching 85.5% of MB discoloration when using 0.25 g L-1 of catalyst at neutral pH with no oxidant needed. Furthermore, PAC-MG demonstrated excellent stability in 6 consecutive cycles. Finally, it is expected that the present study can add value to industrial waste and contribute to the development of novel water and wastewater treatment methods, ensuring water quality for human consumption and the environment.

Efficient removal of sertraline hydrochloride from wastewater using banana peels functionalized: performance adsorption, mechanisms and applicability.

The presence of sertraline hydrochloride (SER) has been detected in water bodies and wastewater, which encourages the search for alternative treatments for its control and removal. Agro-industrial residues are considered efficient adsorbents and functionalization with magnetic nanoparticles improve the adsorptive properties of these materials, in addition to facilitating their separation from a fluid by an external magnetic field. Thus, this study developed and characterized a new material via the functionalization of the banana peel with iron oxide nanoparticles (BANFunc) for the adsorption of SER in batch experiments. Physicochemical and spectroscopic techniques indicated that the BANFunc functionalization method was effective and improved the adsorption capacity (0.68 and 39.96 mg g-1 for BANPure and BANFunc, respectively). The adsorption studies revealed a maximum adsorptive capacity of 142.85 mg g-1 at 240 min and 318 K. Furthermore, the process presented spontaneous and endothermic behaviour, with a better fit to the pseudo-first-order and Langmuir models for the kinetic and isothermal, respectively. The reuse of the biosorbent was effective for five cycles, and even in the 3rd cycle, the adsorbent showed more than 80% SER removal. The adsorption process can be explained by hydrogen bonds and π-interactions. In the synthetic mixture treatment, the biosorbent demonstrated a satisfactory removal rate, of 86.91%, and individual removals of 83.23%, 89.36% and 88.15% for SER, safranine orange and chloroquine, respectively. Therefore, BANFunc is a promising material for large-scale applications, considering its sustainable character and high treatment efficiency.

Cyanobacteria and cyanotoxins in the environment and water intakes: Reports, diversity of congeners, detection by mass spectrometry and their impact on health.

Cyanobacteria are aquatic microorganisms of high interest for research due to the production of secondary metabolites, among which the most popular are cyanotoxins, responsible for causing severe poisoning in humans and animals through ingestion or contact with contaminated water bodies. Monitoring the number of cyanobacteria in water and concentrations of secreted cyanotoxins with the aid of sensitive and reliable methods is considered the primary action for evaluating potentially toxic blooms. There is a great diversity of methods to detect and identify these types of micro contaminants in water, differing by the degree of sophistication and information provided. Mass Spectrometry stands out for its accuracy and sensitivity in identifying toxins, making it possible to identify and characterize toxins produced by individual species of cyanobacteria, in low quantities. In this review, we seek to update some information about cyanobacterial peptides, their effects on biological systems, and the importance of the main Mass Spectrometry methods used for detection, extraction, identification and monitoring of cyanotoxins.

Enhanced filtration membranes with graphene oxide and tannic acid for textile industry wastewater dye removal.

A novel modification technique employing a layer-by-layer (LbL) self-assembly method, integrated with a pressure-assisted filtration system, was developed for enhancing a commercial polyethersulfone (PES) microfiltration (MF) membrane. This modification involved the incorporation of tannic acid (TA) in conjunction with graphene oxide (GO) nanosheets. The effectiveness of the LbL method was confirmed through comprehensive characterization analyses, including ATR-FTIR, SEM, water contact angle (WCA), and mean pore size measurements, comparing the modified membrane with the original commercial one. Sixteen variations of PES MF membranes were superficially modified using a three-factorial design, with the deposited amount of TA and GO as key factors. The influence of these factors on the morphology and performance of the membranes was systematically investigated, focusing on parameters such as pure water permeability (PWP), blue corazol (BC) dye removal efficiency, and flux recovery rate (FRR). The membranes produced with the maximum amount of GO (0.1 mg, 0.55 wt%) and TA as the inner and outer layers demonstrated remarkable FRR and significant BC removal, exceeding 80%. Notably, there was no significant difference observed when using either 0.2 (1.11 wt%) or 0.4 mg (2.22 wt%) in the first layer, as indicated by the Tukey mean test. Furthermore, the modified membrane designated as MF/TA0.4GO0.1TA0.4 was evaluated in the filtration of a simulated dye bath wastewater, exhibiting a BC removal efficiency of 49.20% and a salt removal efficiency of 27.74%. In conclusion, the novel PES MF membrane modification proposed in this study effectively enhances the key properties of pressure-driven separation processes.

Synthesis of a novel functionalized biosorbent from mango stone and its application in the pharmaceutical's removal from water and a synthetic mixture.

This paper explores the feasibility of functionalizing mango stones with iron oxide magnetic nanoparticles (MS-Fe3O4) by coprecipitation in batch adsorption processes. The synthesized material was characterized and applied in chloroquine (CQN) and sertraline hydrochloride (SER) removal from contaminated waters. The biosorbent was subjected to a regenerative study and treatment using a synthetic mixture of contaminants to evaluate its applicability in real effluents. The biosorbent was analyzed by transmission electron microscopy images, scanning electron microscopy, dispersive X-ray spectroscopy, Fourier transform infrared spectra, and zeta potential to characterize its chemical and morphology properties. The techniques applied showed the effectiveness of the proposed modification. In the adsorption experiments, the optimal adsorbent dosage was 0.01 g for both contaminants. The pH strongly influenced the adsorption of the drugs on MS-Fe3O4, and the best results were obtained in the pH range of 5-6. Kinetic data showed a better fit to the pseudo-second-order model, and the equilibrium time was achieved in 16 h for CQN and 4 h for SER. Isotherm studies revealed maximum adsorptive capacities of 49.42 and 64.79 mg g-1, respectively, for CQN and SER, at 318 K, demonstrating that the increase in temperature is a favorable factor, and the Sips model better describes the process. The thermodynamic parameters indicate an endothermic (ΔH° >0), spontaneous (ΔG° <0), and reversible (ΔS° >0) nature of the adsorption. This process is essentially governed by physical forces, such as hydrogen and π-π bonds. However, it is also valid to consider the presence of electrostatic forces due to the ionizing nature of CQN and SER. The MS-Fe3O4 biosorbent showed good performance when evaluated in a synthetic mixture of four contaminants, with an overall removal efficiency of approximately 86% and the regenerative capacity of three reusing cycles.

Innovative Trends in Modified Membranes: A Mini Review of Applications and Challenges in the Food Sector.

Membrane technologies play a pivotal role in various industrial sectors, including food processing. Membranes act as barriers, selectively allowing the passage of one or other types of species. The separation processes that involve them offer advantages such as continuity, energy efficiency, compactness of devices, operational simplicity, and minimal consumption of chemical reagents. The efficiency of membrane separation depends on various factors, such as morphology, composition, and process parameters. Fouling, a significant limitation in membrane processes, leads to a decline in performance over time. Anti-fouling strategies involve adjustments to process parameters or direct modifications to the membrane, aiming to enhance efficiency. Recent research has focused on mitigating fouling, particularly in the food industry, where complex organic streams pose challenges. Membrane processes address consumer demands for natural and healthy products, contributing to new formulations with antioxidant properties. These trends align with environmental concerns, emphasizing sustainable practices. Despite numerous works on membrane modification, a research gap exists, especially with regard to the application of modified membranes in the food industry. This review aims to systematize information on modified membranes, providing insights into their practical application. This comprehensive overview covers membrane modification methods, fouling mechanisms, and distinct applications in the food sector. This study highlights the potential of modified membranes for specific tasks in the food industry and encourages further research in this promising field.

Toxicity assessment of tannery effluent treated by an optimized photo-Fenton process.

In this work, an optimized photo-Fenton process was applied to remove pollutants from tannery industrial effluent (TIE) with its final toxicity level being assessed by a lettuce-seed-based bioassay test. A full 33 factorial design was applied for the optimization of long-term photo-Fenton experiments. The oPtimum conditions of the photo-Fenton process were attained at concentration values of 0.3 g Fe(2+) L(-1) and 20 g H2O2 L(-1) and pH3, for 120 min UV irradiation time. Reactor operating parameter (ROP) effects on the removal of chemical oxygen demand, colour, turbidity, total suspended solids and total volatile solids were evaluated, suggesting that a broad range of ROP values are also suitable to give results very near to those of the photo-Fenton experiments under optimal conditions. Based on the low calculated median lethal dose (LD50) values from a lettuce-seed-based bioassay test, we suggest that recalcitrant substances are present in treated TIE samples. A possible cause of the high toxicity level could partly be attributed to the nitrate concentration, which was not completely abated by the photo-Fenton process. Apart from this, the photo-Fenton process can be used as a part of an industrial effluent treatment system in order to abate high organic pollutant loads.

On the Analysis of Cryogels and Xerogels Using Cellulose Nanofibers and Graphene Oxide.

Aerogels are highly porous and ultralight three-dimensional materials with great potential for various applications. To obtain highly porous and structurally stable aerogels, a carefully designed synthesis process is required. These materials offer flexibility in manipulating their properties, allowing the incorporation of modifying agents according to specific needs. In this study, compounds were synthesized using graphene oxide (GO) and nanocellulose fibers (NFC) through the hydrothermal reduction methodology. Two drying techniques were employed: lyophilization and oven evaporation, resulting in materials called cryogel and xerogel, respectively. Various parameters that can interfere with the properties of these nanomaterials were evaluated. The results indicated that the cryogel dried by lyophilization provided the best applicability due to its structural flexibility after compressions, whereas the xerogel obtained through the oven evaporation process resulted in a compound with high rigidity and disintegration. Structural characterizations demonstrated the successful development of the precursors and promising characteristics in the synthesized nanomaterials. With its flexibility, approximately 98% porosity, low shrinkage rate, light weight, and electrical conductivity, the developed cryogel showed high potential in various applications, such as pressure sensors, electromagnetic shielding, and other research and development fields.

A novel magnetic adsorbent from activated carbon fiber and iron oxide nanoparticles for 2,4-D removal from aqueous medium.

Carbonaceous materials have been widely applied as adsorbents, but there are some factors that affect their efficiency. In this context, advances in nanotechnology provide new and more efficient methodologies for water treatment. This study evaluated the efficiency of a novel carbon-based adsorbent developed from Brazilian polyacrylonitrile textile fiber and functionalized with iron oxide magnetic nanoparticles for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) from the aqueous medium. The synthesized adsorbent (ACF-Fe3O4) was characterized by FTIR, XRD, VSM, Zeta potential, SEM, EDX, and TEM. The characterization techniques showed that the adsorbent has peaks characteristic of its precursors and superparamagnetic characteristics, confirming the efficiency of the synthesis method. The adsorption tests evaluated the influence of adsorbent dosage, pH of the contaminant solution, contact time and temperature on the removal of 2,4-D. The experimental data were better adjusted by the pseudo-second order kinetic model and by the Langmuir isothermal model. The thermodynamic parameters revealed that the process is exothermic, spontaneous and thermodynamically favorable. Under the best experimental conditions, the maximum adsorption capacity obtained was 51.10 mg g-1 with an adsorbent concentration of 0.33 g L-1, natural pH of the solution, temperature of 288 K at the equilibrium time of six hours. Adsorbent reusage was studied in four desorption cycles. The adsorption mechanism can be explained through π-π bonds, hydrogen bonds and electrostatic interactions. The prepared material presented high-efficiency adsorption capacity of 2,4-D compared to other carbonaceous materials present in the literature, demonstrating its viability for the removal of this contaminant from the aqueous medium.

Okara and okara modified and functionalized with iron oxide nanoparticles for the removal of Microcystis aeruginosa and cyanotoxin.

Eutrophicating compounds promote the growth of cyanobacteria, which has the potential of releasing toxic compounds. Alternative raw materials, such as residues, have been used in efficient adsorption systems in water treatment. The aim of the present study was to apply the residue Okara in its original form and modified by hydrolysis with immobilization of magnetic nanoparticles as an adsorbent. For the removal, the cyanobacteria Microcystis aeruginosa was chosen, as well as its secondary metabolites, L-amino acids leucine and arginine (MC-LR microcystin), from aqueous solutions. The adsorbents presented a negative surface charge, and the x-ray diffraction (DRX) outcomes successfully demonstrated the immobilization of iron oxide nanoparticles on the adsorbents. The adsorbent with the best result was the Okara hydrolyzed and functionalized with iron oxide, which showed a 47% (qe = 804.166 cel/g) and 85% (qe = 116.94 µg/L) removal for the cyanobacteria cells and chlorophyll-a, respectively. The kinetics study demonstrated a pseudo-first-order adsorption with maximal adsorption in 480 minutes, removing 761 µg/L of chlorophyll-a. In this trial, a low organic material removal has occurred, with a removal rate of 5% (qe = 0.024 mg/g) in the analysis of compounds in absorbance by ultraviolet light (UV) monitored by optical density determination in 254 nm (OD254). Nevertheless, the reaction system with the presence of organic material removed 53,28% of the MC-LR toxin, with adsorption capacities of 2.84 µg/L in a preliminary trial conducted for two hours, arising as a potential and alternative adsorbent with a capacity of removing cyanobacteria and cyanotoxin cells simultaneously.

Modification of natural zeolite clinoptilolite and ITS application in the adsorption of herbicides.

The clinoptilolite natural zeolites (NZs) posses low herbicide adsorption capacity demanding acid-, alkali-, or salt chemical modifications that enhance its adsorption. However, this may affect the material structure and charge distribution. Alternatively, zeolites may be synthesized at a high cost and time-consuming process. Consequently, new methods, such as the hydrothermal method, for NZ modification needs to be studied. In this sense, a novel surface-modified zeolite (SMZ), using hexadecyltrimethylammonium bromide (CTAB), in acid media was produced by the hydrothermal method and applied for the adsorption of Atrazine (ATZ), Diuron (DIU) and 2,4-D. Commercial NZ and SMZ were characterized by SEM, XRD, TGA, FT-IR, AA spectroscopy, pHPZC, Zeta potential and N2-physisorption. The SMZ chosen for the adsorption experiments was the one with the highest modification yield and adsorption capacity obtained from a complete design of experiments (CTAB=0.74 ; D=12 Mesh; HCl=0.1 M; t=6 h and T=205 ºC). The adsorption experiments revealed that the SMZ adsorption capacity for the herbicide 2,4-D (qmax=9.02 mg/g) was greater than that obtained for ATZ (qmax=2.11 mg/g) and DIU (qmax=1.85 mg/g), which was explained by the presence of the hydroxyl group and by geometric characteristics of the 2,4-D. Adsorption models' fitting showed that the adsorption of 2,4-D onto SMZ were best described by pseudo-second order kinetic (k2=0.005-0.006 g/mg.min; qe,exp=7.122-8.614 mg/g) and Langmuir isothermal model (KL=0.283-0.499 L/mg; qm=7.167-7.995 mg/g). These results indicate that the hydrothermal method is a viable alternative to enable the use of NZs for the adsorption of emerging contaminants from wastewater.