Functionalized silica nanotubes with azo-chromophore for enhanced Pd2+ and Co2+ ions monitoring in E-wastes

Silica nanotubes (SNTs) were utilized as a scaffold for designing a novel solid chemical sensor. The optical nanosensor was designed by direct immobilization of novel azo-chromophore with two carboxylic acid groups called (Z)-2-((2-hydroxynaphthalen-1-yl)diazenyl)terephthalic acid (azo-HNTA) onto the SNTs. Beer's law was obeyed in the ranges of 5-240 and 5-150 ppb for Pd2+ and Co2+ ions, with linear correlation coefficients of 0.999 and 0.971, respectively. The novel nanosensor presented high sensitivity for very low concentrations up to 1.10 x 10(-7) mol L-1 (11.7 ppb for Pd2+). The proficiency of this chemosensor for utilizing as an adsorber was tested. The (azo-HNTA) sensor presented a very quick adsorption property for the elimination of Pd2+ and Co2+ ionswithout preconcentration. The capacities of adsorptionwere 69.83 and 161.03mg/g for Pd2+ and Co2+ ions, respectively. Additionally, this nanosensor has efficient recognition and selective recovery of Pd2+ and Co2+ ions in E-wastes. (C) 2021 Elsevier B.V. All rights reserved.