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"Water Purification"
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Amyloid–carbon hybrid membranes for universal water purification
Industrial development, energy production and mining have led to dramatically increased levels of environmental pollutants such as heavy metal ions, metal cyanides and nuclear waste. Current technologies for purifying contaminated waters are typically expensive and ion specific, and there is therefore a significant need for new approaches. Here, we report inexpensive hybrid membranes made from protein amyloid fibrils and activated porous carbon that can be used to remove heavy metal ions and radioactive waste from water. During filtration, the concentration of heavy metal ions drops by three to five orders of magnitude per passage and the process can be repeated numerous times. Notably, their efficiency remains unaltered when filtering several ions simultaneously. The performance of the membrane is enabled by the ability of the amyloids to selectively absorb heavy metal pollutants from solutions. We also show that our membranes can be used to recycle valuable heavy metal contaminants by thermally reducing ions trapped in saturated membranes, leading to the creation of elemental metal nanoparticles and films.
Hybrid membranes made from protein amyloid fibrils and activated porous carbon can be used to remove heavy metal ions and radioactive waste from water.
Journal Article
Effects of a large-scale distribution of water filters and natural draft rocket-style cookstoves on diarrhea and acute respiratory infection: A cluster-randomized controlled trial in Western Province, Rwanda
Unsafe drinking water and household air pollution (HAP) are major causes of morbidity and mortality among children under 5 in low and middle-income countries. Household water filters and higher-efficiency biomass-burning cookstoves have been widely promoted to improve water quality and reduce fuel use, but there is limited evidence of their health effects when delivered programmatically at scale.
In a large-scale program in Western Province, Rwanda, water filters and portable biomass-burning natural draft rocket-style cookstoves were distributed between September and December 2014 and promoted to over 101,000 households in the poorest economic quartile in 72 (of 96) randomly selected sectors in Western Province. To assess the effects of the intervention, between August and December, 2014, we enrolled 1,582 households that included a child under 4 years from 174 randomly selected village-sized clusters, half from intervention sectors and half from nonintervention sectors. At baseline, 76% of households relied primarily on an improved source for drinking water (piped, borehole, protected spring/well, or rainwater) and over 99% cooked primarily on traditional biomass-burning stoves. We conducted follow-up at 3 time-points between February 2015 and March 2016 to assess reported diarrhea and acute respiratory infections (ARIs) among children <5 years in the preceding 7 days (primary outcomes) and patterns of intervention use, drinking water quality, and air quality. The intervention reduced the prevalence of reported child diarrhea by 29% (prevalence ratio [PR] 0.71, 95% confidence interval [CI] 0.59-0.87, p = 0.001) and reported child ARI by 25% (PR 0.75, 95% CI 0.60-0.93, p = 0.009). Overall, more than 62% of households were observed to have water in their filters at follow-up, while 65% reported using the intervention stove every day, and 55% reported using it primarily outdoors. Use of both the intervention filter and intervention stove decreased throughout follow-up, while reported traditional stove use increased. The intervention reduced the prevalence of households with detectable fecal contamination in drinking water samples by 38% (PR 0.62, 95% CI 0.57-0.68, p < 0.0001) but had no significant impact on 48-hour personal exposure to log-transformed fine particulate matter (PM2.5) concentrations among cooks (β = -0.089, p = 0.486) or children (β = -0.228, p = 0.127). The main limitations of this trial include the unblinded nature of the intervention, limited PM2.5 exposure measurement, and a reliance on reported intervention use and reported health outcomes.
Our findings indicate that the intervention improved household drinking water quality and reduced caregiver-reported diarrhea among children <5 years. It also reduced caregiver-reported ARI despite no evidence of improved air quality. Further research is necessary to ascertain longer-term intervention use and benefits and to explore the potential synergistic effects between diarrhea and ARI.
Clinical Trials.gov NCT02239250.
Journal Article
Rapid removal of organic micropollutants from water by a porous β-cyclodextrin polymer
An alternative material to activated carbon for water remediation is reported: a porous material based on crosslinked cyclodextrins that is better than activated carbons at adsorbing a range of pharmaceuticals, pesticides and other anthropogenic pollutants.
Near-instant removal of organic micropollutants from water
Water purification and remediation is often carried out using various forms of activated carbon; it is inexpensive, but only partially removes many organic pollutants. However, regenerating activated carbon for reuse is energy intensive, requiring high temperatures, and performance decreases upon recycling. Now William Dichtel, Damian Helbling and colleagues have developed an alternative to activated carbon for water remediation: a high-surface-area, mesoporous polymer of β-cyclodextrin. Not only does the material outperform activated carbons at adsorbing a range of pharmaceuticals, pesticides and other pollutants, but it is easily regenerated by washing at room temperature.
The global occurrence in water resources of organic micropollutants, such as pesticides and pharmaceuticals, has raised concerns about potential negative effects on aquatic ecosystems and human health
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. Activated carbons are the most widespread adsorbent materials used to remove organic pollutants from water but they have several deficiencies, including slow pollutant uptake (of the order of hours)
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and poor removal of many relatively hydrophilic micropollutants
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. Furthermore, regenerating spent activated carbon is energy intensive (requiring heating to 500–900 degrees Celsius) and does not fully restore performance
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. Insoluble polymers of β-cyclodextrin, an inexpensive, sustainably produced macrocycle of glucose, are likewise of interest for removing micropollutants from water by means of adsorption
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. β-cyclodextrin is known to encapsulate pollutants to form well-defined host–guest complexes, but until now cross-linked β-cyclodextrin polymers have had low surface areas and poor removal performance compared to conventional activated carbons
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. Here we crosslink β-cyclodextrin with rigid aromatic groups, providing a high-surface-area, mesoporous polymer of β-cyclodextrin. It rapidly sequesters a variety of organic micropollutants with adsorption rate constants 15 to 200 times greater than those of activated carbons and non-porous β-cyclodextrin adsorbent materials
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. In addition, the polymer can be regenerated several times using a mild washing procedure with no loss in performance. Finally, the polymer outperformed a leading activated carbon for the rapid removal of a complex mixture of organic micropollutants at environmentally relevant concentrations. These findings demonstrate the promise of porous cyclodextrin-based polymers for rapid, flow-through water treatment.
Journal Article
Drink more recycled wastewater
There is no room for squeamishness in the face of the world’s growing water shortage — three steps could vastly improve the image of reused water for drinking.
There is no room for squeamishness in the face of the world’s growing water shortage — three steps could vastly improve the image of reused water for drinking.
An engineer makes a routine check of the NEWater membrane process water treatment plant in Singapore
Journal Article
Targeting health subsidies through a nonprice mechanism: A randomized controlled trial in Kenya
Free provision of preventive health products can markedly increase access in low-income countries. A cost concern about free provision is that some recipients may not use the product, wasting resources (overinclusion). Yet, charging a price to screen out nonusers may screen out poor people who need and would use the product (overexclusion). We report on a randomized controlled trial of a screening mechanism that combines the free provision of chlorine solution for water treatment with a small nonmonetary cost (household vouchers that need to be redeemed monthly in order). Relative to a nonvoucher free distribution program, this mechanism reduces the quantity of chlorine procured by 60 percentage points, but reduces the share of households whose stored water tests positive for chlorine residual by only one percentage point, substantially improving the trade-off between overinclusion and overexclusion.
Journal Article