Batch Adsorption of Crystal Violet Onto Acid Pre-Treated Banana Pseudo-Stem Biochar: Effect of Operational Parameters

Abstract

This study investigates the removal of crystal violet (CV) dye from aqueous solutions using biochar derived from locally grown banana  pseudo-stem (BPS). The BPS was cut, air-dried, and then oven-dried at 105°C for 24 h, after which it was converted into biochar through  slow pyrolysis at 300°C for 1 h. For pre-treated biochar (PT biochar), the dried BPS was soaked in 1 M H₂SO₄ for 24 h, rinsed to neutrality,  and subsequently pyrolysed similarly. Batch adsorption experiments were conducted for both types of biochar to assess the effects of pH,  adsorbent dosage, initial dye concentration and contact time. The untreated biochar achieved a maximum CV removal of 96.2% with  adsorption capacities of 12.8 mg/g at a pH of 2, a dosage of 3 g/L, an initial concentration of 40 mg/L, and a contact time of 90 min. The  PT biochar exhibited higher efficiency, with 98.1% removal and an adsorption capacity of 19.6 mg/g at pH 12, a dosage of 2 g/L, an initial concentration of 40 mg/L CV, and a contact time of 60 min. The utilisation of BPS presents a sustainable method for recycling agricultural waste into an eco-friendly, cost-effective, and efficient adsorbent for dye removal. The modification of biochar through acid pre-treatment significantly improves its adsorption performance, highlighting its potential for effective CV removal from water and wastewater, thereby contributing to enhanced water quality and environmental sustainability.