Access to clean drinking water is one of the most significant challenges and is becoming extremely scarce and polluted. Most of the industrial wastewater is discharged into freshwater bodies without adequate treatment, severely polluting the water resources. Various conventional methods have been used to remediate industrial effluents before releasing them into the environment. However, most techniques are not viable in areas with limited resources because of the high cost. Hence, there is an urgent need to develop green, sustainable, and economical alternatives with excellent removal efficiency for industrial wastewater treatment. Keratin has a unique, diverse chemical structure and offers exciting opportunities for modification with advanced biosorption properties. Keratin can be extracted from low-cost biomass sources such as hairs, nails, claws, hooves, wool, horns, and feathers. As a poultry industry by-product, feathers pose severe ecological and commercial issues. Globally, 8–9 million tonnes of chicken feathers are produced yearly. Keratin biopolymer from chicken feathers (keratin >90 %) is one of the viable options for the biosorption of heavy metal ions due to its natural abundance, easy availability and environment-friendly nature. The main objective of this research is to develop an alternative way to use chicken feathers keratin to produce affordable, renewable and sustainable keratin-nanochitosan based biosorbents for industrial wastewater treatment.
Nanochitosan was synthesized by an adapted Calvo et al. method. Chicken feathers (CF) were washed and process to obtain chicken feathers keratin (CFK). Nanochitosan particles (1, 3, and 5 %) on the weight basis of keratin were dispersed using a sonicator for 30 min in 50 ml of distilled water. The keratin-nanochitosan mixture was processed and dried. The dried biosorbents were ground and sieved through 80 μm brass mesh to obtain powdered biosorbents for further structural analysis and biosorption studies. Biosorption studies were conducted with ICP-MS (Perkin Elmer’s Elan 6000) to assess the removal efficiencies of the developed biosorbents and compare them with the neat keratin. The biosorption performance of each sample was investigated with simulated laboratory synthetic wastewater.
The chemical modification of keratin biopolymer with bio-derived nanoparticles can be feasible and sustainable to increase its surface affinity for metal sorption in large-scale applications such as water remediation. The nano-chitosan has polar functional groups such as the hydroxyl group, which can interact with the keratin’s side chains, enhancing the polar and charged side chains on the keratin surfaces and making them more effective for metal removal. It was observed that biosorption of the keratin-nanochitosan derived biosorbents increases with the increase in nanochitosan content. Keratin-nanochitosan derived biosorbents clearly show substantial differences in the surface morphology in contrast with the neat keratin surface. The neat chicken feathers keratin has a fibrous, smooth, homogeneous surface and long shafts. However, the incorporation of nanochitosan turned the keratin surface into a coarse or rough surface. As a result, more sorption sites on the keratin protein matrix were exposed, resulting in greater biosorption towards heavy metal ions. The CFK modified with nanochitosan gave a better biosorption capacity for all metals oxy- anions and cations than neat CFK.
This study demonstrated excellent sorption of heavy metal ions by chicken feathers keratin-nanochitosan derived biosorbents. As a renewable carbon resource, chicken feathers keratin is a promising biosorbent for large-scale remediation of industrial wastewater containing multiple heavy metal cations and anions. In future, optimization of the biosorbent concentration, actual wastewater treatment and biodegradation of the developed biosorbents will be studied to broaden the impact of this research study.
Biosorbents for water remediation were prepared using keratin biopolymer cross-linked with nanochitosan (NC). Keratin proteins were dissolved using reducing agents and NC was incorporated with concentrations of 1, 3 and 5 % individually into the keratin solution. The mixtures were thermally treated at 75 °C overnight, which promoted the formation of ester bonds between the hydroxyl groups of nanochitosan and the carboxylic groups of the keratin biopolymer. The resulting keratin derived biosorbents were characterized by X-Ray photoelectron spectroscopy, confirming the cross-linking between keratin and nanochitosan. The chicken feathers keratin (CFK) surface modifications with nanochitosan were examined with Brunauer-Emmett-Teller, scanning and transmission electron microscopies. The sorption capacity of biosorbents was tested for eight different metals simultaneously at different contact times (15, 30, 60, 120, 240, 280 mins) and pH (5.5, 7.5 and 8.5), including arsenic, selenium, chromium, nickel, cobalt, lead, cadmium and zinc, using simulated industrial wastewater water containing 600 μgl−1 concentration of each metal. The synthesized environmentally benign biosorbents exhibited biosorption of metals upto 98 % at pH 7.5 and a contact time of 24 h, showing their potential for industrial wastewater remediation.
