Ozonation is an efficient process for the primary degradation of most substrates but not for their mineralisation. In this work, the ozonation enhanced with the addition of H2O2 was studied for two substrates with very different oxidation resistances: the dye rhodamine 6G (R6G) and the surfactant linear alkylbenzene sulfonate (LAS). With O3 only, the primary degradation of R6G was completed in less than 10 min but its TOC removal only reached 45% in 1 h. By adding H2O2, TOC removal was increased to 70% with a molar ratio (mol H2O2/mol substrate) of 10. The analysis of pH decrease served to define the specific basicity loss (SBL). The optimum conditions for the R6G mineralisation were found to be associated with a SBL value between 1 and 10 ((min/g)/L)?1, through an adequate addition of H2O2. Moreover, in the case of LAS, the addition of H2O2 for a greater efficiency should occur after the foaming period, above all formed at acid pH. LAS degradation was also considerably improved, and the optimum for primary degradation achieved in 10 min with a TOC removal of over 65% with a molar ratio (mol H2O2/mol substrate) of 20.
Bisphenol A (BPA) and reactive black 5 (RB5) dye are among the most persistent and non-biodegradable contaminants in water which require an urgent need for the development of effective removal method. The ubiquitous existence of both contaminants could interfere with the human health and aquatic environmental balance. Photocatalytic process as one of advanced oxidation processes (AOPs) has shown high performance for degradation of organic compounds to the harmless materials under sensible condition. Therefore, this study aims to develop a visible-light-driven photocatalyst that can efficiently degrade BPA and RB5 present in household water. N-doped TiO2 were successfully synthesized via simple and direct sol–gel method. The prepared TiO2 nanoparticles were characterized by field emission scanning microscope (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Brunauere Emmette Teller (BET) analysis. The incorporation of nitrogen in TiO2 lattice exhibited excellent optical responses to visible region as revealed by UV–Vis–NIR spectroscopy absorption capability at 400–600 nm. The photocatalytic activity of the N-doped TiO2 nanoparticles was measured by photocatalytic degradation of BPA and RB5 in an aqueous solution under visible-light irradiations. Degradation of BPA and RB5 was 91.3% and 89.1%, respectively after 360 min illumination. The degradation of BPA and RB5 by N-doped TiO2 was increased up to 89.8% and 88.4%, respectively under visible-light irradiation as compared to commercial TiO2 P25. This finding clearly shows that N-doped TiO2 exhibits excellent photocatalytic degradation of BPA and RB5 under visible irradiation, hence have a promising potential in removing various recalcitrant contaminants for water treatment to fulfill the public need to consume clean water.
Amine-grafted MSU-3 mesoporous silica samples were synthesized from pure and waste silica sources and their CO2 adsorption performances were evaluated. The obtained samples were characterized using X-ray diffraction (XRD), thermogravimetric analysis (TGA), N2 adsorption–desorption isotherm analysis, Fourier transform infrared (FTIR), and transmission electron microscopy (TEM). CO2 adsorption capacities of the samples at different temperatures were determined by TGA. The amine-modified MSU-3 synthesized from waste exhibited the highest CO2 adsorption capacity of 1.32 mmol/g at 25 °C and 1 bar, depending essentially on the porous texture and the amine content of the material. The CO2 adsorption isotherms of the synthesized samples were measured by a static volumetric method. Adsorption isotherm indicated that the amine-modified samples presented significantly higher CO2 adsorption capacity than the pure samples. The Avrami kinetic model fitted the experimental data well and suggested that complex reaction mechanism or the appearance of multiple reaction pathway occurred in the CO2 adsorption.
It is well-established that aquatic wildlife is exposed to natural and synthetic endocrine disrupting compounds which are able to interfere with the hormonal system. Although advanced oxidation processes (AOPs) have shown to be effective, their application is limited by a relatively high operational cost. In order to reduce the cost of energy consumed in the AOPs, widely available solar energy instead of UV light may be applied either as photocatalytic oxidation or as photosensitized oxidation. The main goal of the present study was to investigate the sunlight photodegradation of paraben mixture. Two processes, namely the photocatalytic oxidation with modified TiO2 nanoparticles and photosensitized oxidation with photosensitive chitosan beads, were applied. The oxidants were identified as singlet oxygen and hydroxyl radicals for photosensitized and photocatalytic oxidation, respectively. The toxicity, as well as ability to water disinfection of both processes under natural sunlight, has been investigated. Application of sunlight for the processes led to degradation of parabens. The efficiency of both processes was comparable. Despite the fact that singlet oxygen is weaker oxidant than hydroxyl radicals, the photosensitized oxidation seems to be more promising for wastewater purification, due to the possibility of chitosan bead reuse and more effective water disinfection.
Heavy metals are a common contaminant in water supplies and pose a variety of serious health risks to nearby human populations. A promising approach to heavy metal decontamination is the sequestration of heavy metal ions in porous materials; however, current technologies involve materials which can be difficult to synthesize, are high-cost, or are themselves potentially toxic. Herein, we demonstrate that rapidly synthesized calcium carbonate (CaCO3) microparticles can effectively remove high quantities of Pb2+, Cd2+, and Cu2+ ions (1869, 1320, and 1293 mg per gram of CaCO3 microparticles, respectively) from aqueous media. The CaCO3 microparticles were characterized with powder X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer–Emmett–Teller (BET) N2 sorption–desorption. It was found that the Ca2+ ions of the microparticles were replaced by the heavy metal ions, leading to partially recrystallized nanoparticles of new compositional phases such as cerussite (PbCO3). The adsorption, surface dissolution/re-precipitation, and nucleation/crystal growth mechanisms were determined by investigating the Ca2+ released, along with the changes to particle morphology and crystal structure. Importantly, this study demonstrates that the porous CaCO3 microparticles performed well in a system with multiple heavy metal ion species: 100% of Cu2+, 97.5% of Pb2+, and 37.0% Cd2+ were removed from an aqueous solution of all cations with initial individual metal concentrations of 50 mg/L and 1.5 g/L of CaCO3 microparticles. At this concentration, the CaCO3 microparticles significantly outperformed activated carbon. These results help to establish CaCO3 microparticles as a promising low-cost and scalable technology for removing heavy metal ions from contaminated water.
Calix[4]arene-crown-6 compounds are promising ligands in the removal of cesium. With this aim, a macrocyclic compound, calix[4]arene-crown-6, was chemically immobilized onto inorganic ordered mesoporous carbon material. Several adsorption parameters such as nitric acid concentration, contact time, initial cesium content, operation temperature, and competing ions were studied. The results demonstrated the prepared material conserved high cesium selectivity of calix[4]arene-crown-6 and physicochemistry stability of the ordered mesoporous carbon matrix and showed the superior cesium adsorption performance. The optimum adsorption acidity determined as 3.0 M nitric acid was consistent with the actual acidity value in the back-end of the nuclear fuel cycle. The Langmuir model indicated the monolayer coverage adsorption and the highest mass adsorption capacity was calculated as 128.06 mg cesium/g. The pseudo-second-order model and D-R model proved the adsorption was a chemical process. Thermodynamics parameters showed the adsorption was spontaneous and exothermal in nature. Competing ions hardly affected cesium adsorption. Furthermore, the adsorbent showed almost intact adsorption capacity after five adsorption-elution cycles. The comprehensive performance highlights the composite material as a promising adsorbent for cesium adsorption from wastewaters.
Artificial sweeteners are food additives widely used, mainly in reduced sugar or sugar-free foods and beverages. Acesulfame potassium (ACE-K) and sodium saccharin (SAC) are among the most widely consumed sweeteners worldwide. These compounds when ingested are not metabolized by the body, being excreted unchanged. They arrive at treatment plants, where they are partially degraded and consequently released directly into water bodies. For this reason, artificial sweeteners have been detected in the most diverse aquatic environments, being recognized as emerging contaminants. In this work, aqueous solutions of ACE-K and SAC, submitted to heterogeneous photocatalysis (TiO2/UV-A) for 60 min, showed degradations of more than 99% and maximum mineralization of 57% for ACE-K and 49% for SAC. The effects of certain variables were evaluated, with pH having a greater influence on the degradation of acesulfame and the mass of semiconductor on that of saccharin. The degradation of ACE-K and SAC followed a pseudo-first-order kinetic model according to the Langmuir–Hinshelwood model. Assays using Artemia salina as the test organism demonstrated the low toxicity of the photocatalyzed solutions of ACE-K and SAC. The contribution of different reactive species to the photocatalysis was investigated using specific radical inhibitors; the results indicate that singlet oxygen (1O2) has a fundamental role in the photocatalytic degradation of ACE-K and SAC.
Paracetamol, the most widely and globally used analgesic and antipyretic, is easily accumulated in aquatic environments. In the present study, the biodegradation of paracetamol in different media (one for general growth, one specific for sulfate reducing bacteria, a mineral salts medium and municipal wastewater) inoculated with two types of sludge (from anaerobic lagoon and from oxidation ditch) under different oxygenic conditions (anoxic; moderate oxygenation in open flasks and high oxygenation by aeration) was investigated. In addition, bacteria with relative abundances increasing simultaneously with paracetamol degradation, when this drug was the only carbon source, thus with a putative role in its degradation, were identified using 16S rRNA gene sequences. The results show that aerobic microorganisms had a major role in the degradation of paracetamol, with 50 mg/L totally removed from municipal wastewater after 2 days incubation with aeration, and that the metabolites 4-aminophenol and hydroquinone plus one compound not identified in this work were produced in the process. The identification of bacteria with a role in the degradation of paracetamol revealed a strain from genus Pseudomonas with the highest final relative abundance of 21.2%, confirming previous works reporting strains of this genus as paracetamol decomposers. Besides, genera Flavobacterium, Dokdonella and Methylophilus were also in evidence, with initial relative abundances of 1.66%, 1.48 and 0.00% (not detected) in the inoculum and 6.91%, 3.80 and 3.83% after incubation, respectively. Therefore, a putative role of these genera in paracetamol biodegradation is suggested for the first time.
This study presents a combination of dispersive liquid-liquid-solidified floating organic drop microextraction (DLLSFODM) and slotted quartz tube (SQT) with conventional flame atomic absorption spectrometry (FAAS) to improve the sensitivity for cadmium determination. A ligand namely 2-(4-methylphenyl)-1H-imidazo-[4,5-f]-[1,10]-phenanthroline which has not been used in trace analyte determination was used to form a cadmium complex. Stepwise optimization of parameters affecting complex formation (pH, ligand, and buffer solution) and extraction (extraction and dispersive solvents, salt effect and mixing) was done to maximize cadmium absorbance. The slotted quartz tube was fitted onto the flame burner and optimized to increase residence time of atoms in the flame. Instrumental parameters such as sample and fuel flow rate were also optimized to further enhance the absorbance signal for cadmium. Using optimal parameters and values, the limits of detection and quantification were determined to be 0.81 and 2.69 μg L?1, respectively. Low percent relative standard deviations (<?6.0%) indicated good precision for both extraction and instrumental measurements. Recovery tests were used to determine the accuracy of the method and the recovery results obtained were between 88 and 113%.
In order to develop surfactant-enhanced remediation for nitrogen heterocyclic compounds (NHCs) (aniline, indole, and quinolone), the solubilization properties of micellar solutions of five surfactants, namely sodium dodecyl sulfate (SDS), rhamnolipid (RL), polysorbate (Tween 80), sorbitan monolaurate (Span 20), and iso-octyl phenoxy polyethoxy ethanol (TX-100) were investigated in this work. The solubilization capacities were quantified using critical micelle concentration (CMC) as well as thermodynamic and kinetic experiments. Besides, nuclear magnetic resonance (1H NMR) spectra were used to infer the locus of NHCs solubilized by SDS and TX-100. The results from the properties of five surfactants indicated that CMC was affected by temperature, while the micellization was spontaneous and could be both endothermic and exothermic based on the type of surfactant and temperature. Furthermore, the difference in compensation temperature was caused by different solubilization mechanism for various surfactants. The solubilization results showed that the solubilization of NHCs in the surfactant solutions followed a pseudo-first-order kinetic model. Meanwhile, the change in proton’s chemical shift depended on the structure of NHCs and the solubilization ability of surfactants. Finally, the orthogonal experiment (L16(43)) was elementarily designed to optimize the solubilization conditions of indole and the results showed that RL could be a better choice for solubilizing NHCs.
To investigate the effect of permeable pavement surface materials (PPSMs) on the influences of pollutant removal in urban storm runoff, six commonly used PPSMs (porous asphalt, porous concrete, cement brick, ceramic brick, sand base brick, and shale brick) were selected and the research was carried out by batch and column experiments. Results indicated that in batch experiments, except for the shale brick, most of the PPSM will release different pollutants continuously with the contact time increasing. Compared with other materials, porous asphalt and ceramic brick could increase the concentration of pollutants in the runoff greatly. With the contact time increased to 48 h, the concentration of NO3-N and TN increased to 13.0 and 23.1 mg/L for ceramic brick and 13.3 and 32.3 mg/L for porous asphalt, respectively. This is mainly due to the artificial activity that accelerates the wear of the PPSM. Furthermore, results showed that PPSM could eliminate pollutants and influenced the removal efficiency greatly in column experiments. Most PPSMs have a noticeable purification effect on different pollutants, among them the purification effect of porous asphalt is the best. The concentrations of COD, NH3-N, and TN are 139.6, 1.32, and 7.79 mg/L in the effluent, respectively. These results may be attributed to the relatively stable environment in column experiments which is more suitable for the removal of pollutants. This study could offer new insight into the transformation of pollutants in damaged PPSM and provide useful guidelines for the better design of permeable pavement system.
Adsorption is acknowledged as effective for the removal of pollutants from drinking water and wastewater. Biochar, as a widely available material, holds promises for pollutant adsorption. So far, biochar has been found to be effective for multiple purposes, including carbon sequestration, nutrient storage, and water-holding capacity. However, its limited porosity restricts its use in water treatment. Activation of biochars, when performed at a high temperature (i.e., 900 °C) and in the presence of certain chemicals (H3PO4, KOH) and/or gases (CO2, steam), improves the development of porosity through the selective gasification of carbon atoms. Physicochemical activation process is appropriate for the production of highly porous materials. As well, the morphological and chemical structure of feedstock together with pyro-gasification operating conditions for the biochar production can greatly impact the porosity of the final materials. The effectiveness of activated biochar as adsorbent depends on porosity and on some functional groups connected to its structure, both of these are developed during activation. This study provides a comprehensive synthesis of the effect of several activated biochars when applied to the treatment of organic and inorganic contaminants in water. Results show that high aromaticity and porosity are essential for the sorption of organic contaminants, while the presence of oxygen-containing functional groups and optimum pH are crucial for the sorption of inorganic contaminants, especially metals. Finally, although activated biochar is a promising option for the treatment of contaminants in water, further research is required to evaluate its performance with real effluents containing contaminants of emerging concern.
The adsorption process is one of the most important techniques of water and wastewater treatment technology. Therefore, there are many methods allowing to improve the effectiveness of these processes based mainly on the chemical modification of adsorbents. However, they are always associated with the necessity of introducing an additional wastes or sewage to the environment. That is why a purpose of the presented was to investigate an innovative and noninvasive adsorption supporting method based on the using of a static magnetic field. The results showed that in the adsorption process of equimolar copper, nickel, and cadmium mixture, a presence of the magnetic field may increase the effectiveness of the process, with respect to copper by more than 40% and a summary molar removal was increased about 11%. However, the effectiveness of the analyzed modification depends largely on the heavy metal equilibrium concentration, and when it increases, a beneficial effect of magnetic field significantly decreases. Nevertheless, due to the fact that heavy metal adsorption processes are very important part of environmental engineering technologies, it can be assumed that further work on magnetic modification of these processes can allow for a significant improvement of many water and wastewater purification plants.
This work examines the rates of bioremediation during a landfarming process. A field study was performed using three types of soil, which were contaminated with two different hydrocarbon concentrations: 20,000 and 50,000 ppm of total petroleum hydrocarbons (TPH). They were subjected to landfarming under the action of different treatments, based on the provision of irrigation, aeration by rototilling, fertilizer, and surfactant. The biodegradation of TPH, considering concentration and families of hydrocarbon compounds (including polycyclic aromatic hydrocarbons, PAHs), was precisely measured for a period of 486 days. The results show how biodegradation rates depend on soil texture, initial contamination level, and type of amendment. Thus, the combination of fertilizer, irrigation, and aeration was the best treatment for treating the soil contaminated with 20,000 ppm of TPH (TPH final concentrations were reduced to a range of 49 to 62% depending on the soil texture). In the case of parcels contaminated with 50,000 ppm of TPH, the most effective treatment combined the supply of fertilizer, surfactant, irrigation, and aeration (TPH final concentrations were reduced to a range of 47 to 63%, depending on the soil texture). The best biodegradation results are obtained for soils with coarser textures and using the treatment with fertilizer, irrigation, and aeration. In addition, the application of surfactant did not imply a significant improvement in the level of biodegradation of hydrocarbons in soil contaminated with 20,000 ppm of TPH, whereas in soils contaminated with 50,000 ppm of TPH, it played a leading role.
A bioadsorbent formulated with a secondary raw material, consisting of grape marc, subjected to a bioxidize process and entrapped in calcium alginate beads, was used for the desalination of water containing copper(II) sulfate. Experiments were established under different experimental conditions varying the concentration of contaminant, the amount of bioadsorbent, and the extraction time through response surface methodology. The most significant variable in the removal of copper(II) sulfate was the amount of bioadsorbent employed, followed by the extraction time; whereas, the adsorbent capacity was more influenced by the amount of contaminant and the amount of bioadsorbent used. At the highest concentration of copper(II) sulfate (0.15 mol/L), the equations obtained predict that the bioadsorbent has a capacity of 2785 mg/g and produces a copper(II) removal about 43% using low adsorbent/water ratios, 1:10 (v/v), and maximum extraction times; whereas, it would remove 97.2% of copper(II) sulfate in 5 min, using adsorbent/water ratios close to 1:2 (v/v), with capacity values, in this case, around 1800 mg/g. The encapsulation of the bioxidize adsorbent increased its capacity to 30% and allowed the precipitation of sulfate ions as calcium sulfate. The results obtained in this work could presume advances for promoting the industrial symbiosis between winery and environmental industries.
Graphical abstract Utilization of secondary raw material, consisting of bioxidize grape marc from winery industry, as bioadsorbent encapsulated in calcium alginate beads, for the removal of copper(II) sulfate from water
Nano zerovalent iron (nZVI) impregnated reduced graphene oxide (nZVI-rGO) hybrid was prepared via gaseous hydrogen reduction of anhydrous iron(III) chloride (FeCl3) on the surface of thermally exfoliated reduced graphene oxide (rGO) nanosheets without using any toxic reducing agent, surfactant, or stabilizing agent. Characterization of prepared samples was carried out using various techniques. Morphological study showed that prepared rGO possesses a few-layered wrinkled paper-like structures and nZVI particles of ~?30 nm size were homogeneously dispersed on the surface of rGO nanosheets. Fourier transform infrared (FTIR), X-ray diffraction (XRD), and energy dispersive X-ray spectrometry (EDS) analyses indicated that oxygen-containing functional groups decreased in the order of graphite oxide (GO) > rGO > nZVI-rGO. Removal studies of trinitrotoluene (TNT) were carried out using graphite (G), GO, rGO, and nZVI-rGO with the aid of high-performance liquid chromatography (HPLC). Kinetic models were applied to establish the rate and mechanism of adsorption of TNT on different adsorbents, and intraparticle diffusion model based on initial adsorption characteristics was employed to ascertain mechanism of film and intraparticle diffusion in the adsorption process. The removal rate and adsorption capacity was found to be highest for nZVI-rGO, which renders this adsorbent to be a potential futuristic adsorbent for removal of explosives.
Ni, Cu, and Ni-Cu metal oxides supported on granular activated carbon (GAC) were synthesized and used in catalytic ozonation of heavy oil produced water. The effect of preparation conditions on their catalyst composition, catalyst structure, and catalytic activity was investigated. The catalyst structure was characterized by X-ray power diffraction (XRD). The results revealed that the Ni-Cu/GAC has the highest catalytic activity, followed by Cu/GAC and Ni/GAC. Metal oxide loading rate depended on impregnation process, whereas dispersion of metal oxides was controlled by calcination process. The XRD analysis showed that the principal active phase was Cu2O for Cu/GAC and Ni-Cu/GAC catalyst and NiO for Ni/GAC catalyst. The most active plane was Cu2O(200) and then followed by Cu2O(110) and Cu2O(111) for Cu-supported catalysts. Higher calcination temperature and time favored the generation of Cu2O but increased the crystalline diameter. It also suggested that promoting the generation of NiO and Cu2O phase and reducing the crystalline diameter could improve the catalytic activity. During Ni-Cu/GAC preparation, existence of Ni(NO3)2 could accelerate the adsorption of Cu(NO3)2, promoting the generation of Cu2O, and improve the dispersion of Cu2O phase.
Developing urbanization, water shortage, watercourse pollution, and demands for more food due to population growth require a more efficient water irrigation and fertilizer application. Retaining nutrients and water in agricultural soils brings about higher crop yields and prevents pollution of water courses. Among different solutions, zeolites, which are environmental friendly, ubiquitous, and inexpensive, have been extensively employed in agricultural activities. These minerals are considered as soil conditioners to improve soil physical and chemical properties including infiltration rate, saturated hydraulic conductivity (Ks), water holding capacity (WHC), and cation exchange capacity (CEC). Natural and surface-modified zeolites can efficiently hold water and nutrients including ammonium (NH4+), nitrate (NO3?) and phosphate (PO43?), potassium (K+), and sulfate (SO42?) in their unique porous structures. Their application as slow-release fertilizers (SRFs) are reported as well. Therefore, zeolite application can improve both water use efficiency (WUE) and nutrient use efficiency (NUE) in agricultural activities and consequently can reduce the potential of surface and groundwater pollution. This review paper summarizes findings in the literature about the impact of zeolite applications on water and nutrient retention in the agriculture. Furthermore, it explores benefits and drawbacks of zeolite applications in this regard.
In this study, the optimum conditions for the ammonia removal from aqueous solution by microwave-assisted air stripping have been investigated at pH 11. Ammonia solution with five different initial ammonia concentrations was prepared synthetically. The Taguchi method was applied to optimize the ammonia removal conditions. Initial ammonia concentration, air flow rate, temperature, stirring speed, microwave radiation power, and radiation time were defined as the optimization parameters. Experiments were carried out at five different levels for each operational parameter. The results of the experiments revealed that 1800 ppm of initial ammonia concentration, 7.5 L min?1 of air flow rate, 60 °C of temperature, 500 rpm of stirring speed, and 500 W of microwave radiation power for 180 min. of microwave radiation time are optimum conditions for complete ammonia removal. In addition to present experimental data, the optimum operational conditions predicted by the balanced characteristics of orthogonal array were confirmed experimentally. Finally, the effect of optimization parameters was discussed in detail.
Biosorbents are the natural origin adsorbents, which popularity in environmental engineering is steadily increasing due to their low price, ease of acquisition, and lack of the toxic properties. Presented research aimed to analyze the possibility of chemical modification of the straw, which is a characteristic waste in the Polish agriculture, to improve its biosorption properties with respect to removal of selected metals from aquatic solutions. Biosorbents used during the tests was a barley straw that was shredded to a size in the range of 0.2–1.0 mm. The biosorption process was performed for aqueous solutions of zinc at a pH 5. Two different modifications of straw were analyzed: esterification with methanol and modification using the citric acid at elevated temperature. The results, obtained during the research, show a clear improvement in sorption capacity of the straw modified by the citric acid. In the case of straw modified with methanol, it has been shown that the effectiveness of zinc biosorption process was even a twice lower with respect to the unmodified straw. Moreover, it was concluded that the removal of analyzed metals was based mainly on the ion-exchange adsorption mechanism by releasing a calcium and magnesium ions from the straw surface to the solution.
