Biopolymer-reinforced synthetic granular nanocomposites for affordable point-of-use water purification

Abstract

Creation of affordable materials for constant release of silver ions in water is one of the most promising ways to provide microbially safe drinking water for all. Combining the capacity of diverse nanocomposites to scavenge toxic species such as arsenic, lead, and other contaminants along with the above capability can result in affordable, all-inclusive drinking water purifiers that can function without electricity. The critical problem in achieving this is the synthesis of stable materials that can release silver ions continuously in the presence of complex species usually present in drinking water that deposit and cause scaling on nanomaterial surfaces. Here we show that such constant release materials can be synthesized in a simple and effective fashion in water itself without the use of electrical power. The nanocomposite exhibits river sand-like properties, such as higher shear strength in loose and wet forms. These materials have been used to develop an affordable water purifier to deliver clean drinking water at US $2.5/y per family. The ability to prepare nanostructured compositions at near ambient temperature has wide relevance for adsorption-based water purification.hybrid | green | appropriate technology | frugal science | developing world S afe drinking water is a significant, but simple indicator of development. Its availability at point of use can save over 2 million human lives (1) (of the 3.575 million deaths caused by water, sanitation, and hygiene issues, 42.6% are due to diarrhea alone: 3.575 million × 0.426 = 1.523 million lives), can avoid over 2 billion diarrheal infections (2), and can contribute over $4 billion to the global gross domestic product (3) (formula used: Σ (number of deaths attributed to diarrhea in each country × corresponding country's per capita gross domestic product). Considering the challenges associated with traditional disinfectants (4), solutions based on state-of-the-art science and technology hold the key for safe drinking water (5) and novel approaches are being looked at (6, 7). It has been long known that silver, especially in nanoparticle form, is an effective disinfectant and works for a wide spectrum of bacteria and viruses (8, 9). Numerous approaches are available for the synthesis of biocidal silver nanoparticles or colloids, including the use of matrices (10-12). The biocidal property of silver nanoparticles, usually in the size range of 10-20 nm, is attributed to the release of trace quantities of silver ions in water (13-16), which, although being sufficient for microorganism killing, does not exhibit toxicity to humans (17,18). [Toxicity due to silver nanoparticles themselves is also known (16)]. Although a number of silver-based biocidal compositions have been synthesized, those have not been able to reach the masses in large volumes (e.g., silver nanoparticleloaded ceramic candles) (19). Massive deployment has been hampered due to the following reasons: (a) Drinking water contains many species (e.g., inorganic ions and organics) that anchor on the sur...

Silver Nanoparticles Decrease the Viability of Cryptosporidium parvum Oocysts

“…Hyperspectral imaging with enhanced dark-field microscopy offers a significantly higher signal-to-noise ratio and therefore better scatter detection of particles than conventional optical methods, and the spectral profiles of NPs can be used to detect NPs by hyperspectral imaging; this method has increasingly been used for the study of environmental samples (18,19,30), including the semiquantitative detection of uptake of NPs by protozoa (19) and the study of disinfection of water samples (31). We employed hyperspectral imaging to study both whether nanoparticles interact with the membrane and the oocyst morphology after exposure.…”

Engineered nanomaterials for water treatment and remediation: Costs, benefits, and applicability

“…A nano-enabled composite point-of-use (POU) water purification system with a two-stage filtration process provides 10 L of clean water in 1 h [496]. The first stage of the process kills viruses and microorganisms while the second stage absorbs chemical pollutants.…”

Efficient removal of arsenic from water using a granular adsorbent: Fe–Mn binary oxide impregnated chitosan bead

“…Moreover, it is inexpensive, biodegradable, biocompatible, and nontoxic to human and environment (Gupta et al, 2009;Miller and Zimmerman, 2010;Sargin et al, 2015). Thus, it has been extensively used as a host material for immobilization of fine powders and nanoparticles (Miller and Zimmerman, 2010;Sarkar et al, 2012;Sankar et al, 2013). Chitosan had been employed for the removal arsenic from water, but it showed rather low sorption capacity for As(V) and even less capacity for As(III) (Elson et al, 1980;Miller and Zimmerman, 2010), which limited its application.…”