[A-GE28] Energy-Environment-Water Nexus and Sustainable Development

[AGE28-P07] Diatom-based novel biosensor for detection of heavy metals recovered from RO Reject water

*Sumit Dhali¹, Rahul Jain¹, Anushree Malik¹, Satyawati Sharma¹, Ramesh Raliya¹ (1.Indian Institute of Technology Delhi)

Keywords:Biosensor, Diatom, Reverse osmosis reject, Heavy metal, Wastewater treatment

Heavy metal contamination is one of the severe problems for both aquatic and terrestrial biota due to its slow biodegradability and biomagnification phenomenon and ultimately warns us of its remediation. Considering the existing analytic techniques, such as atomic absorption spectrometry, Inductively Coupled Plasma Mass Spectrometry, identifying metals in large samples may be labour-intensive and challenge the ability to analyse them quickly. Biosensor having the advantage of specificity, cheap, handy and real-time analysis may help address these issues. In this present study aimed to develop a mesoporous silica-based sensor obtained from domestic reverse osmosis reject (ROR) treated diatom and explore its application in heavy metal ion detection. Diatom, an unfathomed group of unicellular eukaryotic phytoplanktons with enormous potential and capability in modern science, makes diverse applications in wastewater treatment, cosmeceuticals, biosensors, and energy storage. This is the first time diatom directly converted into a biosensor using thermal treatment to detect heavy metals. Diatom Navicula sp. was cultivated in domestic ROR water with silica-enriched ASN-III as a control. On characterisation, ROR was found to contain nitrate-nitrogen (63.6 mgL^-1), total dissolved phosphorous (5.2 mgL^-1), silica (14.7 mgL^-1), pH 7.1. The cultivation experiment was performed using 150 ml working volume at 25 degree Celsius, maintaining a 16:8-h light/ dark cycle for 14 days. ROR proved a promising source of culture media for diatom as the result depicted in terms of growth rate (d = 0.36 per day) and biomass productivity (9.72 mg per litter per day) which was 1.63 and 1.57 times greater than the control, respectively. After harvesting, the diatom was converted to a diatom-biosensor (DBS) using thermal treatment at 750-degree Celsius for 120 minutes. This process removed all the organic matter in the frustule and made them mesoporous, negatively charged, mesoporous, biogenic silica material. The detection of heavy metal ions by DBS was carried out by suspending DBS in the heavy metal cocktail (Cd, Pb, Cr, Co) for 5 minutes and further collecting it by centrifugation. Heavy metal detection was done by the treated DBS using Scanning electron microscopy - energy dispersive X-ray spectroscopy. It was further confirmed by the ICPMS analysis. This developed DBS resulted a quick analysis of heavy metals in an aqueous solution, which can be an effective solution for a large number of sample analyses with minimal resources. This research will help field practitioners utilise such bio sensors from waste materials, resulting in environmental sustainability and circular economy. It also allows researchers to further develop such biosensors using the waste sources like diatoms from ROR.