Adsorptive optimization of green Calotropis gigantea silver nanoparticles: photocatalytic degradation against Congo red and Acid orange 7 dyes arbitrated by sunlight

• Published in: Desalination and water treatment 2021-10, Vol.237, p.181-190
• Main Authors: Arslan, M., Nadeem, Raziya, Jilani, M. Idrees, Javed, Tariq, Javed, Iram
• Format: Article
• Language: English
• Subjects: Acid orange 7; Calotropis gigantea-AgNPs; Congo red; Percentage recyclability; Sunlight
• ISSN: 1944-3986; 1944-3986
• DOI: 10.5004/dwt.2021.27740

A greener method was incorporated to synthesize nanoparticles of noble metal (Ag) from Calotropis gigantea silver nanoparticles (AgNPs) powdered leaf extract using silver nitrate (AgNO3) solution. The fabricated silver NPs were characterized by X-ray diffraction and scanning electron microscopy. The observed average size of silver NPs assessed as 25–35 ± 0.17 nm with intraparticle distancing, possesses a cubic-spherical shape that is stable beyond 6 months without any accruement. The catalytic reduction of Congo red (CR) and Acid orange 7 (AO-7) dyes was observed with green C. gigantea-AgNPs arbitrated by sunlight as well as in absence of sunlight, respectively. Optimization of various parameters (pH, shaking time and dye concentration) was examined by UV-Vis spectrophotometer. C. gigantea-AgNPs catalytic degradation obeys pseudo-second-order kinetics together with a rate constant (K2) in the presence and absence of sunlight and degradation is said to be physical sorption in nature. Isothermal data exhibit a trend of Freu ndlich > Temkin’s > Langmuir with both dyes on the basis of regression (R2) values. The percentage recyclability of C. gigantea- AgNPs gives their peak values in presence of sunlight: 96.11 with CR and 93.89 with AO-7, respectively.