Bacteria immobilized onto carbon nanofiber as a composite for effective removal of arsenic from wastewater

Abstract

Drinking arsenic-contaminated water is one of the major fears for the health of mankind due to its being of highly toxic and carcinogenic substance. In this perspective, the present work is aimed to prepare Enterococcus faecalis (E. faecalis) immobilized onto carbon nanofiber (CNF) as novel composite sorbent and evaluate it adsorption ability for removal of arsenic ions As(III) from aquatic medium. The Fourier Transform Infrared (FTIR) spectroscopy and Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray (EDX) analysis results displayed that the modification of CNF particles with E. faecalis makes more sorptive sites and the surface functional groups for binding arsenic ions. The designing of the experiment (DOE) methodology was applied to assess the effects of experimental factors on the sorption yield and their significance levels. The designing of factorials was utilized to estimate responses and statistical correlation among experimental parameters. The response surface plots exhibited that the response was higher at an optimum level of variables used in the extraction of arsenic. The equilibrium data under optimized sorption conditions (temperature 24 °C, contact time 30 min, biosorbent amount 500 mg/L and pH 5) were studied for Langmuir and Freundlich isotherms and the data were well fitted to the Langmuir isotherm with obtained maximum removal capacity of 255.2 mg g−1 for monolayer As(III) sorption onto E. faecalis/CNF composite. The sorption mechanism for kinetic studies followed the pseudo-second order model with obtained correlation coefficient (R2 = 0.998). Based on characterization and surface functionalities the proposed adsorption mechanism, the hydrogen bonding, π–π and electrostatic attractions were efficient for bisorption of As(III) onto E. faecalis /CNF composite.