Novel algae-mediated biosynthesis approach of chitosan nanoparticles using Ulva fasciata extract, process optimization, characterization and their flocculation performance.

Chitosan nanoparticles (CNPs) are promising biopolymeric nanoparticles with excellent physicochemical, antimicrobial, and biological properties. In this investigation, CNPs were produced using Ulva fasciata biomass extract as a reducing agent. The SEM micrograph revealed that the biosynthesized CNPs appeared to be spheres with a mean size of 32.49 nm. The ζ-potential pattern of CNPs has a single peak at +33.1 mV, indicating a positively charged surface. The X-ray diffraction pattern of the biosynthesized CNPs exhibited three different peaks at 2θ = 25.24, 52.96, and 72.28°. The FTIR analysis identifies various functional groups. The thermogravimetric analyses demonstrate that CNPs have high thermal stability. Additionally, the highest biosynthesis of CNPs (8.96 mg CNPs/mL) was obtained via FCCCD when the initial pH level was 4, Ulva fasciata extract concentration was 45 %, v/v, and chitosan concentration was 0.9 %. Algae-mediated synthesized CNPs were used as coagulating/flocculating agents. By using the jar test, CNPs exhibited superior flocculation performance compared to commercial coagulants like alum, FeCl, and chitosan in bulk form. Further, different parameters were screened, and the maximum flocculating activity (FA) recorded was 83.58 ± 0.47 % at 500 mg/L of CNPs, 1-5 % clay suspension at pH and temperature ranges of 6-8 and 10-80 °C, respectively. CNPs displayed eminent performance in water clarification.