Your browser doesn't support javascript.
Show: 20 | 50 | 100
Results 1 - 20 de 11.542
Filter
1.
Article in English | MEDLINE | ID: mdl-32368892

ABSTRACT

With the rapid worldwide industrial development, large amounts of pollutants such as heavy metals are discharged into the water sources, causing a huge threat to living beings. To mitigate this issue, there is an urgent need for new water treatment strategies. Inspired by a natural shell nacre structure and a multidimensional hybrid concept, we demonstrate multilayered inorganic-organic hybrid membranes using metallic molybdenum disulfide (MoS2) as two-dimensional transition metal dichalcogenide nanosheets and one-dimensional silk nanofibrils for water purification. Because of its possessing negatively charged layers and interaction sites, the hybrid film could adsorb metal ions and dyes from water. The separation performance can be tuned by changing the component ratios of these two nanomaterials. During filtration, due to the reducing effect of the MoS2 nanosheets, precious metal ions are reduced to their nanoparticle form without any further thermal or chemical treatments. In addition to the one-step removal and recovery of metal ions, the hybrid membranes exhibit excellent potential for the determination and removal of different dyes from water. The results of this research can open up an effective and green avenue for water purification and recovery of metal ions dissolved in water.

2.
Chemosphere ; 255: 126966, 2020 May 04.
Article in English | MEDLINE | ID: mdl-32416392

ABSTRACT

We report on the synthesis of unique nanocomposites based on graphene oxide (GO) and oxidized single-wall carbon nanotubes (O-SWCNTs) combined with UiO-66-NH2 and UiO-66-COOH metal-organic frameworks (MOFs) decorated onto Co0·5Ni0·5FeCrO4 spinel magnetic nanoparticles (SMNPs). Novel SMNPs of Co0·5Ni0·5FeCrO4, synthesized for the first time by the sol-gel method, exhibited exceptional thermal stability up to 985 °C. To modify the physicochemical properties of the SMNPs and MOFs, hydrophilic Zr-based MOFs were directly decorated onto the SMNP (MOF-d-SMNP) which led to improved dispersion properties and enhanced the catalytic activity of the SMNP by providing additional functional groups and active catalytic sites, along with surface area expansion. The synthesis and decoration were achieved by a hydrothermal process forming covalent bonding of MOFs onto the SMNPs, using O-SWCNTs and GO monolayers as platforms. Such an approach proved to be more effective than direct mixing of nanoparticles with the platforms, as it reduced the aggregation of nanoparticles and improved the dispersion forces of the MOF-d-SMNP. The MOF-d-SMNP/GO and MOF-d-SMNP/O-SWCNT nanocomposite properties were characterized by XRD, SEM-EDS, HRTEM, FTIR, TGA, gravimetric gas sorption and BET techniques. Performed experiments revealed exceptional adsorption capacity and catalytic activity (the reduction of the toxic pollutant 4-nitrophenol to 4-aminophenol). We demonstrated that novel nanocomposite materials MOF-d-SMNP/GO and MOF-d-SMNP/O-SWCNT showed potential for water treatment and gas sorption applications. Exhibited properties make these materials promising candidates for use in applications requiring, for example, catalytic activity at elevated temperatures.

3.
Am J Trop Med Hyg ; 2020 May 04.
Article in English | MEDLINE | ID: mdl-32372750

ABSTRACT

Approximately two billion people lack access to microbiologically safe drinking water globally. Boiling is the most popular household water treatment method and significantly reduces diarrheal disease, but is often practiced inconsistently or ineffectively. The use of low-cost technologies to improve boiling is one approach with potential for increasing access to safe drinking water. We conducted household trials to evaluate the feasibility and acceptability of water pasteurization indicators (WAPIs) in the Peruvian Amazon in 2015. A total of 28 randomly selected households were enrolled from a rural and a peri-urban community. All households trialed two WAPI designs, each for a 2-week period. Ninety-six percent of participants demonstrated the correct use of the WAPIs at the end of each trial, and 88% expressed satisfaction with both WAPI models. Ease of use, short treatment time, knowledge of the association between WAPI use and improved health, and the taste of treated water were among the key factors that influenced acceptability. Ease of use was the key factor that influenced design preference. Participants in both communities preferred a WAPI with a plastic box that floated on the water's surface compared with a WAPI with a wire that was dipped into the pot of drinking water while it was heating (77% versus 15%, P < 0.001); we selected the box design for a subsequent randomized trial of this intervention. The high feasibility and acceptability of the WAPIs in this study suggest that these interventions have potential to increase access to safe water in resource-limited settings.

4.
Environ Monit Assess ; 192(6): 347, 2020 May 09.
Article in English | MEDLINE | ID: mdl-32388586

ABSTRACT

Monitoring water quality in urban stream is of utmost importance for water resources managers, who are pressured to optimize monitoring schemes in order to reduce costs. The present study aims to use the results of a 2-year-long water quality monitoring program of an urban stream in Portugal to identify improvement opportunities. The urban stream under study was subjected to wastewater treatment plants effluent discharges, leachates from a major sealed landfill, low-class housing effluents, and nonpoint sources of pollution. Contributing watersheds are mostly artificial surfaces and agricultural land, which irrigate directly from the river. River water quality was evaluated on 11 sampling locations for 24 months from October 2013 to September 2015. The present paper describes statistical analysis of the results obtained for 12 physicochemical parameters in order to optimize the monitoring scheme. Cluster analysis detected a seasonal variation in the water quality and a spatial pattern based on the major point sources of pollution. A factor analysis showed that the parameters that mostly contribute to water quality assessment in this urban river are alkalinity, ammonia, electrical conductivity, pH, temperature, and dissolved oxygen. Results suggest that the monitoring efforts-and associated costs-may be reduced by decreasing monitoring frequency, sampling points, and monitored parameters. The statistical analysis described in this study may be replicated in other water quality monitoring programs, providing useful and important information for the systematic and iterative assessment of the adequacy of water quality sampling programs towards a sustainable management of water quality surveillance.

5.
Article in English | MEDLINE | ID: mdl-32390416

ABSTRACT

Activated carbon (AC) is a low-cost, highly porous material with large internal surface areas. They are highly efficient to absorb moisture and a variety of chemical pollutants. Therefore, it has been widely used in air and water purification. However, the strong affinity to moisture often dominates, thus limiting AC's adsorption capacity of other pollutants in a humid environment and reducing its overall lifetime. In the study, superhydrophobic and anti-moisture activated carbon (SA-AC) pellets are fabricated through one-step modification of commercially available AC with a solution consisting of superhydrophobic silica nanoparticles. The SA-AC pellets exhibit excellent water-repellency with a static water contact angle reaching 160.3°. More importantly, they are moisture-resistant and air permeable. Therefore, they preferably adsorb organic gases at humid conditions. The absorbed organic vapor can be released when they are transferred back to dry atmosphere, for example, releasing approximately 35% of absorbed ethanol. The recoverability significantly reduces energy requirement compared to calcination or conventional extraction. Great adsorption capacity of organic dyes such as methylene blue, removal of oil-in-water microemulsions, and recyclability of SA-AC pellets are demonstrated. The morphology of the microporous structures of the SA-AC pellets is characterized against processing conditions, surface functional groups and hierarchical structures tailored by the deposition of low-surface-energy silica nanoparticles. The resulting micro/sub-micropores on the pellet surface promotes droplet condensate, thus, displaying greater damp-proof performance than those treated by traditional modification. The study here presents a promising alternative for the efficient purification on large-scale air/water treatment.

6.
Sci Total Environ ; 725: 138512, 2020 Apr 06.
Article in English | MEDLINE | ID: mdl-32302853

ABSTRACT

Karst systems, as well as springs, are vulnerable to water perturbation brought by infiltration. In this research, sources of water perturbations were examined. The first objective is to provide a method that can determine the origin of the water flowing in the karst outlet. The second objective is to identify the associated water quality hazards caused by the infiltration source. The method relies on these parameters: turbidity, DOC, NO3-, particle size, and bacteria (E. coli, enterococcus and total coliforms). As the method was applied during flood events, measurement of the water flow is also needed to have a basic knowledge on the hydrodynamic of the water resource. The proposed method is based on a high resolution monitoring of physico chemical parameters of the water flowing during flood events. Using this proposed method, (1) the origin of the water can be identified, (2) the type and nature of water perturbation can be described, and (3) the type of water perturbation that accompanies contaminants such as the one with anthropogenic source (e.g. NO3-) and bacterial nature can be determined. In identifying the water origin, this proposed method employed NO3- and DOC data normalization. Values are projected in the NO3-_norm = f(DOC_norm) reference frame. These are aligned to the slope. Depending on the obtained slope (α), water origin can be disclosed. If α > 1, the increase of concentration of DOC weighs more, characterizing water from surface runoff. Whereas, if α < 1, the consideration is more on the increase of NO3- concentration, characterizing water from unsaturated zone. However if α cannot be calculated because there is no evident slope, this characterizes the water already present in the system. Water originating from the surface runoff is prone to inorganic and bacterial contamination adsorbed by the particles. Identifying the type of water perturbation needing water treatment is important in managing the water resource. Hence, the evolution through time of NO3- and DOC with the particle size distribution, anthropogenic nature type of contaminant (i.e. in this study NO3-), and presence or absence of bacteria were examined. This method was applied in the springs of the Toulon, an important drinking water source of the city of Périgueux in France. This site was chosen considering the following factors: (1) its karst nature being vulnerable to infiltrations, having fractures and sinkholes; (2) its land use being influenced by the anthropogenic activities such as agriculture; and (3) its observed pronounced turbidity incidence. The first flood events of two hydrological cycles were assessed. Three water origins of the spring water and the respective water quality hazards were identified: (i) water from saturated zone with minerals, (ii) water from unsaturated zone with nitrate, and (iii) water from surface runoff with the presence of bacteria. The second and third types of water perturbation gave evidence that the Toulon springs can be contaminated. Hence, in terms of resource management, the information obtained can be used as a basis in forecasting and planning the management actions or water quality treatments needed.

7.
Acc Chem Res ; 53(4): 812-821, 2020 Apr 21.
Article in English | MEDLINE | ID: mdl-32281372

ABSTRACT

ConspectusThe Industrial Revolution has resulted in social and economic improvements, but unfortunately, with the development of manufacturing and mining, water sources have been pervaded with contaminants, putting Earth's freshwater supply in peril. Therefore, the segregation of pollutants-such as radionuclides, heavy metals, and oil spills-from water streams, has become a pertinent problem. Attempts have been made to extract these pollutants through chemical precipitation, sorbents, and membranes. The limitations of the current remediation methods, including the generation of a considerable volume of chemical sludge as well as low uptake capacity and/or selectivity, actuate the need for materials innovation. These insufficiencies have provoked our interest in the exploration of porous organic polymers (POPs) for water treatment. This category of porous material has been at the forefront of materials research due to its modular nature, i.e., its tunable functionality and tailorable porosity. Compared to other materials, the practicality of POPs comes from their purely organic composition, which lends to their stability and ease of synthesis. The potential of using POPs as a design platform for solid extractors is closely associated with the ease with which their pore space can be functionalized with high densities of strong adsorption sites, resulting in a material that retains its robustness while providing specified interactions depending on the contaminant of choice.POPs raise opportunities to improve current or enable new technologies to achieve safer water. In this Account, we describe some of our efforts toward the exploitation of the unique properties of POPs for improving water purification by answering key questions and proposing research opportunities. The design strategies and principles involved for functionalizing POPs include the following: increasing the density and flexibility of the chelator to enhance their cooperation, introducing the secondary sphere modifiers to reinforce the primary binding, and enforcing the orientation of the ligands in the pore channel to increase the accessibility and cooperation of the functionalities. For each strategy, we first describe its chemical basis, followed by presenting examples that convey the underlying concepts, giving rise to functional materials that are beyond the traditional ones, as demonstrated by radionuclide sequestration, heavy metal decontamination, and oil-spill cleanup. Our endeavors to explore the applicability of POPs to deal with these high-priority contaminants are expected to impact personal consumer water purifiers, industrial wastewater management systems, and nuclear waste management. In our view, more exciting will be new applications and new examples of the functionalization strategies made by creatively merging the strategies mentioned above, enabling increasingly selective binding and efficiency and ultimately promoting POPs for practical applications to enhance water security.

8.
Water Res ; 176: 115733, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32234606

ABSTRACT

Urban disaster response requires disposal of complex wastes. This study regards a case wherein high intensity rainfall fell over a remote mountainous area previously burned by wildfire, generating debris flows that devastated a downstream town. Sanitary sewers and homes with septic systems were damaged, releasing human waste into the debris flow field. Contaminated sediments, with their high fecal indicator bacteria (FIB) concentrations, were cleared from public rights-of-way and creek channels by local authorities, then disposed onto distant Goleta Beach for beach nourishment, causing immediate surf zone microbiological water quality exceedances. To determine potential public health threats, disposed sediments and surf zone waters were sampled and analyzed-relative to reference samples of mountain soil and raw sewage-for FIB, pathogens, human (HF183) and other host- (Gull2 TaqMan, and DogBact) associated DNA-based fecal markers, and bacterial community 16S rRNA gene sequences. Approximately 20% of disposed sediment samples contained the HF183 marker; sequencing suggested that all samples were contaminated by sewage. In an initial sediment disposal period, surf zone waters harbored intestinal bacterial sequences that were shared with disposed sediments and sewage. Yet surf zone bacterial communities returned to mostly marine clades within weeks. Taken together, multiple conventional and DNA-based analyses informed this forensic assessment of human waste contamination. In the future, similar analyses could be used earlier in disaster response to guide sediment disposal decisions towards continuously protecting beachgoer health.


Subject(s)
Water Microbiology , Water Quality , Cities , Feces , Geologic Sediments , Humans , RNA, Ribosomal, 16S
9.
Water Res ; 176: 115702, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32247998

ABSTRACT

The degree to which a technology used for drinking water treatment physically removes or inactivates pathogenic microorganisms is commonly expressed as a log-reduction (or log-removal) and is of central importance to the provision of microbiologically safe drinking water. Many evaluations of water treatment process performance generate or compile multiple values of microorganism log-reduction, and it is common to report the average of these log-reduction values as a summary statistic. This work provides a cautionary note against misinterpretation and misuse of averaged log-reduction values by mathematically proving that the average of a set of log-reduction values characteristically overstates the average performance of which the set of log-reduction values is believed to be representative. This has two important consequences for drinking water and food safety as well as other applications of log-reduction: 1) a technology with higher average log-reduction does not necessarily have higher average performance, and 2) risk analyses using averaged log-reduction values as point estimates of treatment efficiency will underestimate average risk-sometimes by well over an order of magnitude. When analyzing a set of log-reduction values, a summary statistic called the effective log-reduction (which averages reduction or passage rates and expresses this as a log-reduction) provides a better representation of average performance of a treatment technology.


Subject(s)
Drinking Water , Water Purification
10.
Water Res ; 176: 115743, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32272321

ABSTRACT

In order to understand and minimize the formation of halogenated disinfection by-products (DBPs), it is important to investigate how dissolved organic matter (DOM) contributes to their generation. In the present study, we analysed the DOM profile of water samples from the Barcelona catchment area by high resolution mass spectrometry (HRMS) and we studied the changes after chlorination. Chlorination produced significant changes in the DOM, decreased the average m/z and Kendrick mass defect (KMD) of their spectra and decreased the number and abundance of lignin-like features. The Van Krevelen (VK) fingerprint exhibited several noticeable changes, including the appearance of highly oxidized peaks in the tannin-like region (average O/C, 0.78 ± 0.08), the appearance of features with low H/C and the disappearance of more than half of the lipids-like features. Up to 657 halogenated peaks were generated during sample chlorination, most of which in the condensed hydrocarbons-like and the lignin-like region of the VK diagram. Around 200 features were found to be strongly correlated (ρ ≥ 0.795) to the formation potential of trihalomethanes (THMs) and 5 were correlated with the formation potential of haloacetonitrile (HANs). They all were plotted in the lignin fraction of the VK diagram, but both groups of features exhibited different nitrogen content: those features related to HANs FP had at least one nitrogen atoms in their structures, whilst those related to THMs did not.


Subject(s)
Disinfectants , Water Pollutants, Chemical , Water Purification , Disinfection , Halogenation , Mass Spectrometry , Trihalomethanes
11.
Water Res ; 176: 115766, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32272324

ABSTRACT

Humic substance is a ubiquitous class of natural organic matter (NOM) in soil and aquatic ecosystems, which severely affects the terrestrial and aquatic environments as well as water-based engineering systems by adsorption on solids (e.g., soil minerals, nanoparticles, membranes) via different interaction mechanisms. Herein, the chemical force microscopy (CFM) technique was employed to quantitatively probe the intermolecular forces of humic acid (HA, a representative humic substance) interacting with self-assembled monolayers (SAMs, i.e., OH-SAMs, CH3-SAMs, NH2-SAMs and COOH-SAMs) in various aqueous environments at the nanoscale. The interaction forces measured during approach could be well fitted by the extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory by incorporating the hydrophobic interaction. The average adhesion energy followed the trend as: NH2-SAMs (∼3.11 mJ/m2) > CH3-SAMs (∼2.03 mJ/m2) > OH-SAMs (∼1.38 mJ/m2) > COOH-SAMs (∼0.52 mJ/m2) in 100 mM NaCl at pH 5.8, indicating the significant role of electrostatic attraction in contributing to the HA adhesion, followed by hydrophobic interaction and hydrogen bonding. The adhesion energy was found to be dependent on NaCl concentration, Ca2+ addition and pH. For the interaction between NH2-SAMs and HA, their electrostatic attraction at pH 5.8 turned to repulsion under alkaline condition which led to the sudden drop of adhesion energy. Such results promised the adsorption and release of HA using the recyclable magnetic Fe3O4 nanoparticles coated with (3-aminopropyl)tiethoxysilane (APTES). This work provides quantitative information on the molecular interaction mechanism underlying the adsorption of HA on solids of varying surface chemistry at the nanoscale, with useful implications for developing effective chemical additives to remove HA in water treatment and many other engineering processes.


Subject(s)
Humic Substances , Water Purification , Adsorption , Ecosystem , Soil
12.
J Environ Manage ; 266: 110579, 2020 Jul 15.
Article in English | MEDLINE | ID: mdl-32310120

ABSTRACT

This study used a relatively long-term (350 d) continuous flow test to determine the bioturbation effect of a benthic macroinvertebrate (the snail Bellamya aeruginosa) on sediment internal phosphorus (P) pollution control by in-situ immobilisation using drinking water treatment residue (DWTR) as the inactivating agent. The results showed that DWTR substantially reduced P concentration in overlying water, had a limited effect on other overlying water properties, and tended to reduce nitrogen release from the sediment. Variations in overlying water properties induced by DWTR were generally not associated with snail activity or population density. However, the snails were found to promote DWTR burial and induce DWTR mixing within the sediment, indicating that bioturbation could change the distribution of P inactivating agents in sediment. The mobility of P was closely related to oxalate extractable aluminium, iron, and P (Alox, Feox, and Pox, respectively) in sediments at different depths. Typically, mobile P was stable at a relatively low level when the total content of Alox and Feox was >0.750 mmol g-1 or when the ratio of Pox to (Alox + Feox) was <0.05. Given these results, recommended practices include repeated dosing of the immobilising agents at intervals determined by the relationships among mobile P, Pox, Alox, and Feox in the sediment, especially for Al- and Fe-based agents such as DWTR. Overall, the effect of bioturbation on the stability of in-situ P immobilisation in sediment should be fully considered during long-term pollution control.


Subject(s)
Drinking Water , Water Pollutants, Chemical , Water Purification , Animals , Eutrophication , Geologic Sediments , Lakes , Phosphorus , Pseudomonas aeruginosa , Snails
13.
Article in English | MEDLINE | ID: mdl-32345011

ABSTRACT

Considering the complexity of toxic ingredients in practical polluted water, the development of energy- and labor-saving and environmentally friendly multifunctional materials to decontaminate wastewater is of great necessity. Herein, a multifunctional branched poly(ethylenimine) (bPEI) and poly(acrylic acid) (PAA)/tungsten oxide/polyacrylonitrile (PP/WO3/PAN) composite membrane was fabricated by the combination of blow spinning and layer-by-layer methods. The incorporated WO3 in generated in hydrophilic PAN fibers by spinning the precursor method, which simultaneously reveals remarkable photodegradation performance towards mimetic organic pollutions and excellent antibacterial activity due to their electron synergetic effect. In addition, the micro/nanoporous structure of the PP/WO3/PAN composite membrane also ensures its good oil-water separation performance. Moreover, the reduction reaction of W atoms in the WO3 network upon solar irradiation endows the membrane with superior heavy metal ion removal capability. Significantly, the membrane exhibits water-enabled self-healing performance due to the coated polyelectrolyte layer. More importantly, the membrane could be easily scaled-up; was free-standing, durable, and biocompatible; and exhibited no additional toxic effect on the surrounding environments. These outstanding properties make the membrane to have significant potential applications in wastewater treatment.

14.
Water Environ Res ; 92(5): 644-645, 2020 May.
Article in English | MEDLINE | ID: mdl-32307764
15.
Chemosphere ; 254: 126821, 2020 Apr 16.
Article in English | MEDLINE | ID: mdl-32325351

ABSTRACT

Since MXenes (a new family of two-dimensional materials) were first produced in 2011, they have become very attractive nanomaterials due to their unique properties and the range of potential industrial applications. Numerous recent studies have discussed the environmental applications of different MXenes in adsorption, catalysis, and membranes. Only a limited number of MXene-based membrane studies have been published to date, and most have discussed only specific MXenes (i.e., Ti3C2Tx), a small number of solutes (e.g., dyes and inorganic salts), and laboratory-scale short-term experiments under limited water-quality and operational conditions. In addition, to our knowledge, there has been no review of MXene-membrane studies. It is therefore essential to assess the current status of understanding of the performance of these membranes in liquid separation and water purification. Here, a comprehensive literature review is conducted to summarize the current preparation techniques for MXene-based membranes and their applications, particularly in terms of environmental and industrial applications (e.g., water treatment and organic solvent filtration), and to direct future research by identifying gaps in our present understanding. In particular, this review focuses on several key factors, including the effects of preparation techniques on membrane properties, operational conditions, and compound properties that influence liquid separation during MXene-based membrane filtration.

16.
Water Res ; 176: 115729, 2020 Jun 01.
Article in English | MEDLINE | ID: mdl-32240845

ABSTRACT

Recreational water quality guidelines protect the public from health risks associated with water recreation by helping to prevent unacceptable concentrations of pathogenic organisms in ambient water. However, illness risk is associated with both the concentration of pathogens in the water and the degree of contact with those pathogens. Different recreational activities can result in different levels of contact with ambient water containing water-borne pathogens. We conducted a systematic literature review and meta-analysis to evaluate risks of illness associated with different recreational activities and different levels of contact to ambient surface waters. We screened 8,618 potentially relevant studies for quantitative measures of risk using inclusion/exclusion criteria established in advance. We categorized recreational activities as swimming, sports-related contact, minimal contact, and sand contact. We combined relative risks using a random effects meta-analysis for adverse health outcome categories representing gastrointestinal illness, respiratory illness, skin, eye, ear, nose, throat, and cold/flu illness. We identified 92 studies meeting our inclusion criteria. Pooled risk estimates indicate significant elevation of gastrointestinal illness with the recreational activity categories swimming (2.19, 95% CI: 1.82, 2.63) and sports-related contact (2.69, 95% CI: 1.04, 6.92), and nonsignificant elevation of gastrointestinal illness with minimal contact (1.27, 95% CI: 0.74, 2.16). We also found a significant elevation of respiratory illness with swimming (1.78, 95% CI: 1.38, 2.29) and sports-related contact (1.49, 95% CI: 1.00, 2.24), and no elevation of respiratory illness with minimal contact (0.90, 95% CI: 0.71, 1.14). This study suggests that exposures associated with different types of recreational activities are important characteristics of the exposure pathway when assessing illness risk associated with recreation in ambient surface waters.


Subject(s)
Swimming Pools , Water Microbiology , Recreation , Risk Assessment , Swimming , Water Quality
17.
J Environ Manage ; 262: 110347, 2020 May 15.
Article in English | MEDLINE | ID: mdl-32250822

ABSTRACT

The increasing use of pharmaceutical products also increases their release in aquatic environment. These contaminants are considered emerging pollutants, and induce adverse ecological and human health effects. The antidiabetic metformin is one example that has been detected in the aquatic environment at unusual concentrations. This fact indicates that conventional wastewater treatment is inefficient on eliminating this compound. Here we show that metformin can be effectively removed from water by photocatalysis. We found the optimised conditions for pH and concentration of catalyst on the photocatalytic process. TiO2 and TiO2-ZrO2 were successful in oxidising metformin under UV radiation following a pseudo-first order kinetics. Intermediates of metformin photodegradation appeared after photocatalytic treatment. Toxicity analysis showed that the degradation products are non-toxic to Lactuca sativa seeds.


Subject(s)
Metformin , Water Pollutants, Chemical , Water Purification , Catalysis , Humans , Kinetics , Photolysis , Titanium , Ultraviolet Rays , Water
18.
J Environ Manage ; 262: 110352, 2020 May 15.
Article in English | MEDLINE | ID: mdl-32250823

ABSTRACT

The management of abundant drinking water treatment sludge (DWTS) in landfill remains an important issue. The reuse of DWTS as construction material could contribute to the development of greener concrete product and to mitigating the detrimental environment effect from excessive production of DWTS. This paper investigates the potential of using DWTS as sand replacement in Concrete Paving Blocks (CPB). Five CPB mixtures were designed and the replacement ratios of sand by DWTS were 0%, 5%, 10%, 15%, and 20%, by weight. Properties of CPB such as compressive strength, water absorption, abrasion resistance, sulfate attack and metal leachability were determined. The results indicated that above 10% of DWTS, the replacement was detrimental to such properties of the CPB. Microstructure analysis proved the addition of DWTS could result in ettringite formation and the interfacial transition zone (ITZ) between the cement matrix and DWTS was more porous than that of sand. In addition, the metal leachability test of CPB demonstrated that the addition of high-copper DWTS into CPB was safe.


Subject(s)
Drinking Water , Water Purification , Construction Materials , Sewage , Waste Disposal Facilities
19.
Toxicon ; 180: 18-27, 2020 Jun.
Article in English | MEDLINE | ID: mdl-32278765

ABSTRACT

The presence of potent hepatotoxic cyanotoxins such as nodularin (NOD) in drinking water, groundwater, surface water, seawater and recreational waters presents a major risks to human and environmental health. Human exposure to cyanotoxins could lead to various health effects such as liver damage, jaundice, neurotoxicity and gastroenteritis. Therefore, it is critical to investigate their occurrence in environmental matrices. This study reports the use of tyre-based activated carbon (WTAC) as an adsorbent for preconcentration and removal of nodularin from environmental matrices prior to high performance liquid chromatographic analysis. The preconcentration and adsorption experiments were carried out in presence of other environmental components to consider the external effect on WTAC adsorption of nodularin. Under optimum conditions, the linear dynamic range was 0.05-70 µg L- 1 with a correlation coefficient of 0.9991. The LOD and LOQ (n = 10) in the absence and in the presence of humic acids were 0.012-0.025 µg L- 1 and 0.040-0.083, n = 10), respectively. The repeatability (n = 10) and reproducibility (n = 5) of the method expressed as relative standard deviation (%RSD) were 3.7 and 5.1%, respectively. The maximum adsorption capacity of WTAC was 345 µg g -1. Furthermore, the results demonstrated that the presence of humic acid has an effect on the nodularin adsorption to WTAC. However, high concentrations other coexisting ions such a Cl-, NO3-, PO43-, HCO3-, SO42- had no significant the effect on the adsorption process. The proposed technique was then used for a preconcentration and elimination of NOD trace levels in different water matrices. The results showed that the WTAC was an effective adsorbent for the preconcentration and removal of NOD from the complex matrices.


Subject(s)
Environmental Monitoring , Peptides, Cyclic/analysis , Water Pollutants, Chemical/analysis , Adsorption , Charcoal/chemistry , Fresh Water/chemistry , Seawater/chemistry , Waste Water/chemistry , Water Purification/methods
20.
Water Sci Technol ; 81(2): 265-273, 2020 Jan.
Article in English | MEDLINE | ID: mdl-32333659

ABSTRACT

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.


Subject(s)
Moringa oleifera , Water Purification , Escherichia coli , Humans , Plant Extracts , Seeds , Water
SELECTION OF CITATIONS
SEARCH DETAIL