Chemical modification, characterization, and application of chicken feathers as novel biosorbents

The current work exclusively pertains to preparing arsenic removing biosorbents using chicken feathers (CF) as a raw material. CF consist of keratinous proteins with many functional groups, and this paper contributes to the debate on how functional groups, especially -COOH, -NH2 and -S-S-, interact with arsenic species before and after their modification through sorption phenomena. Chemically modified CF biosorbents were investigated regarding their ability to remove As(III) from water. The modification results suggest that reactions occur mainly on the surface with noticeable changes on reactive sites in the interior of the modified chicken feathers (MCF). To prepare the modifications labelled as MCF-I and MCF-II, the feathers were treated with aqueous NaOH and sodium sulfite, respectively, to change their structure and morphology. Then, maleimide terminated poly(N-isopropylacrylamide) (PNIPAM) was added to the reaction mixture to enhance the mass and reactivity of the biosorbents. However, MCF-I and MCF-II displayed a relatively low sorption capacity (>= 25-50%) for the removal of arsenic, but a higher capacity than raw CF. The methyl alcohol supported modification MCF-III, on the other hand, exhibited a significant performance in segregating negatively charged arsenic species from water. Therefore, esterified carboxylic groups (-COOH) in keratin were identified as particularly effective promoters of the arsenic uptake. Around 80-90% sorption capacity was observed within the first hour of contact between the MCF-III biosorbent and arsenic polluted water. Characterizations such as FTIR, XRD, DSC, TGA and SEM supported the modification of chicken feathers and the subsequent effect of this modification on the sorption, particularly when MCF-III was applied as a biosorbent. The role of pH was highly significant for changing the surface behaviour, and high uptake was observed at low pH for MCF-I, MCF-II and MCF-III. The kinetics of the biosorption capacities of CF, MCF-I, MCF-II and MCF-III were also evaluated and compared at different pH. The experimental kinetic data for MCF-III at variable pH followed pseudo second order model fits and are typical for chemisorption. Similarly, the Freundlich isotherm model supports our data with a high correlation value (R-2) and demonstrates both monolayer and multilayer biosorption.