scholarly journals Monitoring the lead-and-copper rule with a water-gated field effect transistor

2020 ◽  
Vol 18 (2) ◽  
pp. 159-171 ◽  
Author(s):  
Zahrah Alqahtani ◽  
Nawal Alghamdi ◽  
Martin Grell
Keyword(s):  
Drinking Water ◽  
Thin Film Transistor ◽  
Threshold Shift ◽  
Ion Concentration ◽  
Global Network ◽  
Sensor Technology ◽  
Sno2 Thin Film ◽  
Pvc Membrane ◽  
Lead And Copper Rule ◽  
Action Levels

Abstract We use the natural zeolite clinoptilolite as the sensitive element in a plasticised PVC membrane. Separating a sample pool and a reference pool with such a membrane in water-gated SnO2 thin-film transistor (SnO2 WGTFT) leads to membrane potential, and thus transistor threshold shift in response to the common drinking water pollutants Pb2+ or Cu2+ in the sample pool. Threshold shift with ion concentration, c, follows a Langmuir–Freundlich (LF) characteristic. As the LF characteristic shows the steepest slope in the limit c → 0, this opens a window to limits-of-detection (LoDs) far below the ‘action levels’ of the ‘lead-and-copper rule’ for drinking water: Pb2+: LoD 0.9 nM vs 72 nM action level, Cu2+: LoD 14 nM vs 20.5 μM action level. LoDs are far lower than for membranes using organic macrocycles as their sensitive elements. Threshold shifts at the lead and copper action levels are more significant than shifts in response to variations in the concentration of non-toxic co-cations, and we discuss in detail how to moderate interference. The selective response to lead and copper qualifies clinoptilolite-sensitised WGTFTs as a low footprint sensor technology for monitoring the lead-and-copper rule, and to confirm the effectiveness of attempts to extract lead and copper from water. This article has been made Open Access thanks to the generous support of a global network of libraries as part of the Knowledge Unlatched Select initiative.

scholarly journals Influence of Active Channel Layer Thickness on SnO2 Thin-Film Transistor Performance

Electronics ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 200
Author(s):  
Do Won Kim ◽  
Hyeon Joong Kim ◽  
Changmin Lee ◽  
Kyoungdu Kim ◽  
Jin-Hyuk Bae ◽  
...  
Keyword(s):  
Thin Film ◽  
Field Effect ◽  
Thin Film Transistor ◽  
Sol Gel ◽  
Precursor Concentration ◽  
Sno2 Thin Film ◽  
Field Effect Mobility ◽  
Si Substrates ◽  
Channel Layer ◽  
Active Channel

Sol-gel processed SnO2 thin-film transistors (TFTs) were fabricated on SiO2/p+ Si substrates. The SnO2 active channel layer was deposited by the sol-gel spin coating method. Precursor concentration influenced the film thickness and surface roughness. As the concentration of the precursor was increased, the deposited films were thicker and smoother. The device performance was influenced by the thickness and roughness of the SnO2 active channel layer. Decreased precursor concentration resulted in a fabricated device with lower field-effect mobility, larger subthreshold swing (SS), and increased threshold voltage (Vth), originating from the lower free carrier concentration and increase in trap sites. The fabricated SnO2 TFTs, with an optimized 0.030 M precursor, had a field-effect mobility of 9.38 cm2/Vs, an SS of 1.99, an Ion/Ioff value of ~4.0 × 107, and showed enhancement mode operation and positive Vth, equal to 9.83 V.

Assessment of the drinking water quality for planning endogenic prevention of dental caries

2021 ◽  
Vol 21 (2) ◽  
pp. 88-93
Author(s):  
A. B. Shashmurina ◽  
O. L. Mishutina ◽  
V. R. Shashmurina
Keyword(s):  
Drinking Water ◽  
Dental Caries ◽  
Water Supply ◽  
Fluoride Concentration ◽  
Water Hardness ◽  
Drinking Water Supply ◽  
Ion Concentration ◽  
Normal Range ◽  
Hydrogen Ion Concentration ◽  
Normal Limits

Relevance. Dental caries is a leading dental disease in children. Aim – to study the quality of drinking water in Smolensk and its region to provide evidence for implementing dental caries preventive measures in children.Materials and methods. We took tap water samples from ten water intake points in seven districts of Smolensk and six Smolensk regions. An accredited testing laboratory of the Center for Hygiene and Epidemiology in the Smolensk Region carried out water chemical analysis. The study analyzed standard parameters of drinking water quality: pH 6.5-8.5, fluoride content 0.60-1.2 mg/l; water hardness 7.0-9.0 (Sanitary Regulations and Standards 2.1.4.1116-02). The parameter was considered normal if its 95% confidence interval was within the reference range.Results. In Smolensk, the hydrogen ion concentration in centralized drinking water supply systems is within normal limits and amounts to 7.39 (95% CI: 7.32-7.46; р < 0,05) pH units. The mean fluoride concentration in the Smolensk water is 0.19 (95% CI: 0.14-0.23; р < 0,05) mg/l, which is below the normal range. In most Smolensk districts, water hardness is within normal limits, 8.21 mmol/l (95% CI: 7.03-9.39; р < 0,05). However, the upper limit of the confidence interval of 9.39 mg/l and the maximum of 12.0 mg/l exceed the normal range. In the Smolensk region cities, the hydrogen ion concentration is 7.2 (95% CI: 7.02-7.38; р < 0,05) pH units in the centralized drinking water supply. The fluoride concentration in the Smolensk region water is 0.45 mg/l (95% CI: 0.23-0.68; р < 0,05), which demonstrates the fluoride deficiency in water. In the Smolensk region cities, mean water hardness is 6.66 mmol/l (95% CI: 6.00-7.03; р < 0,05), which is below the normal values. However, the CI upper limit of 7.03 mmol/l and the maximum of 7.05 mmol/l are within normal limits.Conclusions. The water of the centralized drinking water supply system in Smolensk and the Smolensk region is low in fluorides. Urgent community and individual preventive measures should be taken to expose children to fluoride.

scholarly journals Turbidity reduction in drinking water by coagulation-flocculation with chitosan polymers

2019 ◽  
Vol 17 (2) ◽  
pp. 204-218 ◽  
Author(s):  
Ampai Soros ◽  
James E. Amburgey ◽  
Christine E. Stauber ◽  
Mark D. Sobsey ◽  
Lisa M. Casanova
Keyword(s):  
Drinking Water ◽  
Functional Groups ◽  
Dose Range ◽  
Optimal Dose ◽  
Global Network ◽  
Point Of Zero Charge ◽  
Household Water ◽  
Generous Support ◽  
Higher Doses ◽  
Model Household

Abstract Turbidity reduction by coagulation-flocculation in drinking water reduces microbes and organic matter, increasing effectiveness of downstream treatment. Chitosan is a promising household water coagulant, but needs parameters for use. This study tested the effects of chitosan dose, molecular weight (MW), degree of deacetylation (DD), and functional groups on bentonite and kaolinite turbidity reduction in model household drinking water. Higher MW or DD produced greater reductions. Highest reductions were at doses 1 and 3 mg/L by MW &gt;50,000 or &gt;70% DD (residual turbidity &lt;5 NTU). Higher doses did not necessarily continually increase reduction. For functional groups, 3 mg/L produced the highest reductions by lactate, acetate, and HCl, and lower reductions of kaolinite than bentonite. Doses where the point of zero charge was observed clustered around 3 mg/L. Chitosan reduced clay turbidity in water; effectiveness was influenced by dose, clay type, MW, DD, and functional groups. Reduction did not necessarily increase with MW. Bentonite had a broader effective dose range and higher reduction at the optimal dose than kaolinite. Chitosans with and without functional groups performed similarly. The best of the studied doses was 3 mg/L. Chitosans are promising for turbidity reduction in low-resource settings if combined with sedimentation and/or filtration. This article has been made Open Access thanks to the generous support of a global network of libraries as part of the Knowledge Unlatched Select initiative.

scholarly journals Effect of Chloride Ions on the Point-of-Use Drinking Water Disinfection Performance of Porous Ceramic Media Embedded with Metallic Silver and Copper

Water ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1625
Author(s):  
Rekha Singh ◽  
Woohang Kim ◽  
James A. Smith
Keyword(s):  
Drinking Water ◽  
Porous Ceramic ◽  
Chloride Ion ◽  
Silver Ions ◽  
Chloride Ions ◽  
Ion Concentration ◽  
Metallic Silver ◽  
E Coli ◽  
Ion Concentrations ◽  
Copper Release

This study quantifies the effects of chloride ions on silver and copper release from porous ceramic cubes embedded with silver and copper and its effect on E. coli disinfection in drinking water. Log-reduction of E. coli by silver ions decreased after 4 h of contact time as the chloride ion concentration increased from 0 to 250 mg/L but, it was not changed by copper ions under the same conditions. For silver addition by silver-ceramic cubes, log reductions of E. coli decreased sharply from 7.2 to 1.6 after 12 h as the chloride concentration increased from 0 to 250 mg/L. For the silver-ceramic cube experiments, chloride ion also reduced the total silver concentration in solution. After 24 h, total silver concentrations in solution decreased from 61 µg/L to 20 µg/L for corresponding chloride ion concentrations. According to the MINTEQ equilibrium model analysis, the decrease in disinfection ability with silver embedded ceramic cubes could be the result of precipitation of silver ions as silver chloride. This suggests that AgCl was precipitating within the pore space of the ceramic. These results indicate that, although ionic silver is a highly effective disinfectant for E. coli, the presence of chloride ions can significantly reduce disinfection efficacy. For copper-ceramic cubes, log reductions of E. coli by copper embedded cubes increased from 1.2 to 1.5 when chloride ion concentration increased from 0 to 250 mg/L. Total copper concentrations in solution increased from 4 µg/L to 14 µg/L for corresponding chloride ion concentrations. These results point towards the synergistic effect of chloride ions on copper oxidation as an increased concentration of chloride enhances copper release.

scholarly journals Does self-reported water collection time differ from observed water collection time? Evidence from the Upper West Region of Ghana

2020 ◽  
Vol 10 (2) ◽  
pp. 357-365
Author(s):  
Alfred Dongzagla ◽  
Abraham Marshall Nunbogu ◽  
Nicholas Fielmua
Keyword(s):  
Developing Countries ◽  
Drinking Water ◽  
Open Access ◽  
Global Network ◽  
Round Trip ◽  
Key Indicator ◽  
West Region ◽  
Water Collection ◽  
Generous Support ◽  
Collection Time

Abstract Water collection time is a key indicator in tracking access to drinking water. Over the years, water surveillance agencies have relied on water collectors for information on water collection time to measure progress of water supply. However, emerging evidence shows that water collection times reported by water collectors in developing countries are often imprecise. To contribute to knowledge about the validity or otherwise of self-reported water collection times, this study explored the association between self-reported water collection times and observed water collection times in the Upper West Region of Ghana. Data on water collection times were gathered from 412 water collectors in Daffiama-Issa-Bussie District and Lawra Municipality, first through interviews, and second by observation. From the results, self-reported water collection times were significantly (P &lt; 0.01) lower than observed water collection times. The average round-trip water collection time reported by water collectors (32 minutes) was 8 minutes lower than observed water collection times (40 minutes). This implies that existing statistics on basic water coverage that are largely based on self-reported water collection times are overestimated. Going forward, we call on water surveillance agencies to collect data on water collection times through observation. This article has been made Open Access thanks to the generous support of a global network of libraries as part of the Knowledge Unlatched Select initiative.

Influence of extraction properties of PVC plasticizer membrane on the response of coated wire type ion selective electrode

1988 ◽  
Vol 53 (5) ◽  
pp. 912-920 ◽  
Author(s):  
Emil Halámek ◽  
Tomáš Čapoun ◽  
Jan Souček
Keyword(s):  
Distribution Coefficient ◽  
Electrode Potential ◽  
Ion Pair ◽  
Ion Selective Electrode ◽  
Ion Concentration ◽  
Pvc Membrane ◽  
Potential Range ◽  
Selective Electrode ◽  
Coated Wire ◽  
Extraction Properties

The authors studied the influence of the extraction properties of a PVC membrane plasticizer of a coated-wire type ion-selective electrode on its response in titrations of brucine and atropine with sodium tetraphenyl borate, as well as in potentiometric determinations of these compounds. The highest attainable value of the ion pair concentration in the plasticizer, which is limited by the distribution coefficient of the ion pair, determines the interval in which the electrode potential can be changed; and a linear dependence of the potential range of the titration curves on the logarithm of the ion-pair distribution coefficient was found. The slope of the dependence of the electrode potential on the logarithm of the ion concentration to be determined, found in potentiometric measurements, is proportional to the distribution coefficient of the ion which forms a pair with the ion to be determined and in whose solution the electrode membrane is activated between the measurements. The dependence of the slope of the electrode function on the logarithm of the product of the mentioned distribution coefficients is linear.

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