Biomass-Based Silica/Calcium Carbonate Nanocomposites for the Adsorptive Removal of Escherichia coli from Aqueous Suspensions

Abstract

The present study deals with the adsorptive removal of Escherichia coli (E. coli) by making use of chitosan-silica/calcium carbonate (CS-SiO2/CaCO3) nanocomposites (NCs) where it was synthesized using the waste eggshells and rice husks occurred by natural sources. The bioadsorbent CS-SiO2/CaCO3 NCs were synthesized by incorporating eggshell-CaCO3 nanoparticles (NPs) and rice husk-SiO2 NPs in chitosan NPs solution. The adsorbents were characterized using HRTEM, BET, DLS, and TGA. The characterization of NCs revealed the formation of adsorbents in the range of 10–50 nm and some structural changes to the spectra of adsorbents before and after the adsorption of E. coli was revealed by the FTIR analysis. Moreover, the adsorption efficiency of E. coli over the adsorbents after 35 min of incubation was about 80% for CS-SiO2/CaCO3 NCs. Further, the kinetics of adsorption studies were observed to be well-fitted to the Langmuir isotherm model with an adsorption capacity of 3.18 × 101 (CFU E. coil per gram of CS-SiO2/CaCO3). From the analysis, the synthesized bioadsorbent demonstrated the potential for ameliorating the inherent risk of pathogens in water.

Biosorption of Escherichia coli Using ZnO-Trimethyl Chitosan Nanocomposite Hydrogel Formed by the Green Synthesis Route

“…From the short interaction time, the kinetic study, as shown in Figure 4c, was observed to best follow the pseudo-second-order mechanism with rate constant and removal rate of 2.5 × 10 8 CFU g −1 and 6.3 × 10 23 CFU min −1 , respectively. This demonstrated the highest level of linearity (0.9555) in comparison with the determination by the first-order adsorption model (0.9488), thereby predicting chemisorption as the rate-limiting step describing the adsorption processes [52], thus serving as the best kinetic model to describe the adsorption of E. coli onto TM@ZnO/TMC NC hydrogel, supporting the claim of pseudo-second order, describing the equilibrium of E. coli adsorption onto the surface of NC hydrogel [2,53].…”

“…For the E. coli adsorption study onto ZnO/TMC NC, a modified protocol described in Bwatanglang et al [2] was adopted. A known concentration of TM@ZnO/TMC NC hydrogel in a media containing cultured bacterial cell lines (E. coli) in nutrient broth (NB) was first incubated at 35 • C for 24 h at 100 rpm under continuous shaking conditions.…”

“…The uptake capacity (CFU/g) of the sorbents for each concentration of E. coli at equilibrium was determined from the equation qe (CFU/g) = [Ci − Ce) /M] × V, where V is the volume of the solution in L, while M is the mass of biosorbent (g). The kinetic and adsorption mechanisms were determined using the relationships described in Ojediran et al [6] and Bwatanglang et al [2]. The parameters are presented in Table 3.…”

“…This contact of metal NPs such as silver (Ag), gold (Au), zinc (Zn), copper (Cu), titanium (Ti), manganese (Mn), cobalt (Co), etc., with that of biological cells causes a series of intracellular pathways such as oxidative stress, metabolic changes, protein fragmentations, etc. The biomolecules such as lipopolysaccharide, lipoteichoic acid, protein, and phospholipid bilayers on the bacteria cells were reported to dominate the NP-cell adhesion mechanism by either through their highly charged structure and/or through the bridging effect of their surface functional groups [1,2]. This mechanism was reported to govern the NPs-bacterial interactions in studies investigating the antimicrobial susceptibility, adhesion, and adsorption behavior towards the metal oxide NPs surface [1].…”