Ephraim Igberase
Department of Chemical Engineering, Durban University of Technology, Steve Biko, Durban, South Africa.
Innocentia G. Mkhize
Department of Chemical Engineering, Durban University of Technology, Steve Biko, Durban, South Africa.
In this post, we present a brief overview of our recently published book chapter titled “Methylene Blue Adsorption Utilizing Enhanced Chitosan Beads: A Response Surface Methodology and Artificial Neural Network Study.”
High-quality chemicals from Sigma-Aldrich in South Africa were used in the experiment, including sodium hydroxide, acetic acid, hydrochloric acid, epichlorohydrin, MB, and Polyethylene Glycol (PEG). The purity level of these compounds was 99%. A pH meter was used to change the mixture’s pH level. An Ultima 888 water distiller was used to produce distilled water. Adsorption experiments were conducted using an incubator shaker.
1.0 g of MB was dissolved in 1 litre of filtered water to create the MB stock solution with a 1000 mg/L concentration. The adsorbate-containing solution was diluted with distilled water to get the necessary starting concentrations.
The initial step in creating the adsorbent is to dissolve the chitosan powder in an acidic solution, like acetic acid, until a homogeneous chitosan solution is developed. This approach makes it easier to produce beads. The coagulation bath is then prepared using an alkaline solution, such as sodium hydroxide (NaOH). The chitosan solution is then progressively added, drop by drop, to the coagulation bath while continuously stirring. The chitosan molecules gel and precipitate due to the alkaline coagulation bath’s pH rapidly rising in reaction to the acidic chitosan solution. Within the coagulation bath, spherical chitosan beads form due to the ionic interactions between the chitosan and the counterions in the solution. After forming, the generated chitosan beads (CH) are thoroughly cleaned with deionised water to remove any salt, acid, or other impurities. This cleaning process is essential to maintaining the CS integrity and purity. The produced CS was cross-linked by exposing the beads to a 1M epichlorohydrin solution and stirring them for two hours. For grafting PEG onto the cross-linked chitosan beads (CCS), they were exposed to microwave radiation for half an hour. The produced adsorbent was washed with distilled water to eliminate any last bits of unreacted compounds. Following cleaning, the grafted cross-linked chitosan beads (GCCS) are typically freeze-dried for 24 hours using a Scanvac coolsafeTM freeze-drier to eliminate excess moisture and provide the desired shape. A Micromeritics (Australia) Tristar 3000 analyser was used to quantify the samples’ BET surface area, pore volume, and pore size using nitrogen adsorption at 77 K. A Cu kα radiation source in a Phillips X’pert Model 0993 was used for the X-ray diffraction (XRD) study. At a scanning rate of 0.4°C per minute, the diffraction intensity was measured between 5º and 90º (2θ).