Biosorption of basic violet 10 onto activated Gossypium hirsutum seeds: Batch and fixed-bed column studies

Abstract

Sulphuric acid activated immature Gossypium hirsutum seed (AIGHS) was prepared to biosorbe basic violet 10 (BV10) from aqueous solutions. Methylene blue number, iodine number and Brunauer–Emmett–Teller surface analysis indicated that the AIGHS were hetero-porous. Boehm titrations and Fourier-transform infrared spectra demonstrated the chemical heterogeneity of the AIGHS surface. Batch biosorption studies were used to examine the effects of process parameters in the following range: pH2–12, temperature 293–313K, contact time 1–5h and initial concentration 200–600mg·L−1. The matching of equilibrium data with the Langmuir–Freundlich form of isotherms indicated that the BV10 was adsorbed via chemisorption and pore diffusion. Kinetic investigation indicated multiple order chemisorption through an Avrami kinetic model. Film diffusion controlled the rate of BV10 biosorption onto AIGHS. The spontaneous and endothermic nature of sorption was corroborated by thermodynamic study. Continuous biosorption experiments were performed using a fixed-bed column and the influence of operating parameters was explored for different ranges of initial concentration 100–300mg·L−1, bed height 5–10cm, and flow rate 2.5–4.5ml·min−1. A dose response model accurately described the fixed-bed biosorption data. An external mass transfer correlation was formulated explaining BV10-AIGHS sorption.