Potentiality of Rod-Type Chitosan Adsorbent Derived from Sewage Sludge

The potential use of wastewater sludge as a biosorbent for the removal of various metals and metalloids from aqueous solutions was investigated. The sludge was immobilized in a rod shape with chitosan to improve sorption capacity and solid–liquid separation ability. An optimal condition for the production of rod-shaped chitosan-immobilized sludge (RCS) was determined by considering the biosorbent production potential and As(V) removal efficiency. The optimal sludge and chitosan contents and RCS thickness were 6.0%, 4.0%, and 0.2–0.3 mm, respectively. The anion removal performance of RCS was investigated for As(V), Cr(VI), and Mn(VII), and the cation removal performance was investigated for Cd(II). Pseudo-first-order and pseudo-second-order models adequately explained the kinetic data for the RCS, while the Langmuir and Freundlich models explained the equilibrium data for the RCS. These results showed that RCS has a higher adsorption capacity for anions than for cations. The results also indicated that electrostatic attraction or ion exchange is the main mechanism for metal/metalloid removal by RCS, except for the case of Mn(VII) where an adsorption-coupled reduction mechanism may be suggested