No abstract

Arsenicosis was recognized over 104 years ago. Elevated arsenic (As) concentrations in water is faced by about 200 million people worldwide and has become one of the biggest challenges in the context of water purification. Providing sustainable and affordable solutions to tackle this menace is a need of the hour. Adsorption on advanced materials is increasingly being recognized as a potential solution. Here, we report various functionalized microcellulose-reinforced 2-line ferrihydrite composites which show outstanding As­(III) and As­(V) adsorption capacities. Green synthesis of the composite yields granular media with high mechanical strength which show faster adsorption kinetics in a wide pH range, irrespective of the presence of other interfering ions in water. The composites and their interaction with As­(III) and As­(V) were studied by XRD, HRTEM, SEM, XPS, Raman, TG, and IR spectroscopy. Performance of the media in the form of cartridge reaffirms its utility for point-of-use water purification. We show that cellulose microstructures are more efficient than corresponding nanostructures for the purpose of arsenic remediation. We have also performed an evaluation of several sustainability metrics to understand the “greenness” of the composite and its manufacturing process.

Fluoride (F–) is one of the common naturally occurring anions present in groundwater worldwide that may be beneficial or detrimental depending on the total amount ingested and the duration of exposure. Among all the remediation techniques, adsorption using nanomaterials shows superior efficiency and the process can be eco-friendly and economical. We report cellulose nanofiber-polyaniline (PANI)-templated ferrihydrite nanocomposite synthesized by a green one-pot process where the iron precursor not only acts as an oxidant for the polymerization of aniline to give emaraldine base–emaraldine salt (EB–ES) form of PANI but also forms 2-line ferrihydrite (FeOOH) nanoparticles in situ. These nanoparticles get embedded into the cellulose–PANI blend to give a granular nanocomposite having double action sites for adsorption and robustness which also prevent nanoparticle leaching. Doped PANI and FeOOH act as synergistic adsorption sites for F– removal which results in an enhanced uptake capacity. The materials’ adsorption mechanism and removal performance have been evaluated by diverse analytical techniques. The investigations led to the conclusion that the material is suitable to be used as adsorption media in the form of simple cartridges for gravity-fed water purification. In addition, the impact of such materials on the environment has been assessed by evaluating the relevant sustainability metrics and socio-economic parameters.

Higher levels of fluoride (F – ) in groundwater constitute a severe problem that affects more than 200 million people spread over 25 countries. It is essential not only to detect but also to accurately quantify aqueous F – to ensure safety. The need of the hour is to develop smart water quality testing systems that would be effective in location-based real-time water quality data collection, devoid of professional expertise for handling. We report a cheap, handheld, portable mobile device for colorimetric detection and rapid estimation of F – in water by the application of the synthesized core–shell nanoparticles (near-cubic ceria@zirconia nanocages) and a chemoresponsive dye (xylenol orange). The nanomaterial has been characterized thoroughly, and the mechanism of sensing has been studied in detail. The sensor system is highly selective toward F – and shows unprecedented sensitivity in the range of 0.1–5 ppm of F – , in field water samples, which is the transition regime, where remedial measures may be needed. It addresses multiple issues expressed by indicator-based metal complexes used to determine F – previously. Consistency in the performance of the sensing material has been tested with synthetic F – standards, water samples from F – affected regions, and dental care products like toothpastes and mouthwash using a smartphone attachment and by the naked eye. The sensor performs better than what was reported by prior works on aqueous F – sensing.