Design of chitosan and watermelon (Citrullus lanatus) seed shell composite adsorbent for reactive orange 16 dye removal: multivariable optimization and dye adsorption mechanism study

• Published in: BIOMASS CONVERSION AND BIOREFINERY
• Main Authors: Agha, Hasan M.; Jawad, Ali H.; Alothman, Zeid A.; Wilson, Lee D.
• Format: Article; Early Access
• Language: English
• Published: SPRINGER HEIDELBERG 2024
• Subjects: Energy & Fuels; Engineering
• Online Access: https://www-webofscience-com.uitm.idm.oclc.org/wos/woscc/full-record/WOS:001405191500001

Herein, chitosan (CS) and watermelon seed shell (WSS) were blended to yield a new biocomposite (CS/WSS) via sonication with an ultrasonic bath of 40 kHz for 25 min at 20 W. Thus, CS/WSS adsorbent was applied for the removal of reactive orange 16 dye (RO16) from the aqueous environment. The CS/WSS characteristics were evaluated using XRD, SEM-EDX, FTIR, and pHpzc methods. The adsorption efficiency of CS/WSS with the RO16 dye was optimized using a Box-Behnken design (BBD). The three independent experimental parameters include the CS/WSS dosage (A 0.02-0.1 g/100 mL), contact time (B 10-60 min), and RO16 solution pH (C 4-10). The kinetics of adsorption analysis validates that the adsorption of RO16 with the CS/WSS biocomposite adopts a pseudo-second-order (PSO) adsorption profile. In addition, the Freundlich and Langmuir isotherm models were assessed to obtain best-fit results for the isotherm profiles. The maximum adsorption capacity of CS/WSS biocomposite (qmax) for RO16 was found to be 158.6 mg/g in an acidic pH environment at pH 4 and 25 degrees C. The mechanism of RO16 adsorption onto the CS/WSS biocomposite surface has several contributions that include electrostatic forces, hydrogen bonding, n-pi and pi -pi interactions. Thus, the CS/WSS biocomposite exhibits favourable RO16 dye removal in aqueous media.