No abstract

Metallic iron (Fe 0 )-based filtration systems have the potential to significantly contribute to the achievement of the United Nations (UN) Sustainable Development Goals (SDGs) of substantially improving the human condition by 2030 through the provision of clean water. Recent knowledge on Fe 0 -based safe drinking water filters is addressed herein. They are categorized into two types: Household and community filters. Design criteria are recalled and operational details are given. Scientists are invited to co-develop knowledge enabling the exploitation of the great potential of Fe 0 filters for sustainable safe drinking water provision (and sanitation).

Since the realization in the 1930s that elevated fluoride concentrations in drinking water can have detrimental effects on human health, new methods have been progressively developed in order to reduce fluoride to acceptable levels. In the developing world the necessity for filtration media that are both low-cost and sourced from locally available materials has resulted in the widespread use of bone char. Since the early 1990s metallic iron (Fe 0 ) has received widespread use as both an adsorbent and a reducing agent for the removal of a wide range of contaminant species from water. The ion-selectivity of Fe 0 is dictated by the positively charged surface of iron (hydr)oxides at circumneutral pH. This suggests that Fe 0 could potentially be applied as suitable filter media for the negatively charged fluoride ion. This communication seeks to demonstrate from a theoretical basis and using empirical data from the literature the suitability of Fe 0 filters for fluoride removal. The work concludes that Fe 0 -bearing materials, such as steel wool, hold good promise as low-cost, readily available and highly effective decentralized fluoride treatment materials.

Researchers on metallic iron (Fe 0

No abstract

Several studies have reported various defluoridation capabilities of plant biomasses. The resultant variations in fluoride removal capacities are associated with the presence of different types of active functional groups in the respective biomasses. This study reports of the fluoride removal efficiencies of sisal leaf biomass in comparison. Comparison with other plant biomasses were made and hence the fluoride removal efficiencies of maize leaf (ML), goose grass (GG), banana false stem (BFS), Aloe vera (AV), untreated sisal fibre (USF) and sisal pith (SP) with similar active functional groups but different stereochemistry and solubility of the active compounds are reported. A portion of 0.5 g of each biomass was mixed with a 10 mg/l fluoride solution in a 10 ml portions under the same experimental conditions. The maximum fluoride removal capacity of sisal fibre biomass was found to be 26.6 %. By comparison, the fluoride removal efficiencies of ML, GG, BFS, AV, USF and SP were found to be, 4.1, 4.6, 7.1, 26.6, 29.4 and 47.3 % respectively. This suggests that, stereochemistry and solubility of the active compounds have a significant role to play in water defluoridation by plant biomasses, and thus, knowledge of the stereochemistry and solubility of the active compounds in plant biomass is very important to fully unlock biomass' defluoridation potentials.

The use of iron (Fe) (III) salts as fluoride coagulants in water is challenged by the requirement of high pH for maximum efficiency. At their natural pH, these salts have low fluoride removal efficiency. This study examines the effect of amaranth plants on enhancement of the defluoridation efficiency of Fe (III) salts as coagulants. Amaranthus hybridus plants were suspended in fluoride water treated with varying concentrations of Fe (III) with its roots immersed completely in fluoride water for varying time from 720 to 1440 min. The study shows that fluoride coagulation by Fe (III) in the absence of plants is limited to 10%, whereas when plants were introduced, it increased from 10 to 40%. These results suggest that amaranth plants enhance the defluoridation efficiency of Fe (III). This enhanced removal may be attributed to increased coagulation effected by exudates released by plant root which contain organic compounds and CO 2 or charged root surfaces by the formation of Fe (III) oxide film. The exact factor that has a major contribution to enhanced removal observed remains to be subject of further studies.