Preparation and characterization of activated carbon from pineapple waste biomass for dye removal

• Preparation and characterization of activated carbon were conducted using one type of less-studied agricultural waste namely pineapple waste biomass.
• Of the three types of pineapple waste biomass, pineapple leaves instead of harder plant parts namely pineapple stem and crown, had highest surface area.
• Methylene blue profiles showed good fit towards adsorption isotherm models and can be well explained using the kinetic models.

Environmental pollutions from pigment-containing wastewaters from various industrial sources are of concern nowadays. Conventional treatment techniques are efficient but sometimes create secondary pollution that requires further disposal. Utilization of agricultural waste biomass such as from the pineapple (Ananas comosus) industry offers an interesting alternative based on its potential to be converted into activated carbon. In this study, activated carbon was prepared from the pyrolysis (500 °C, 1 h) of pineapple waste biomass (leaves, stem, crown) impregnated with ZnCl2. Resulting activated carbon with the highest surface area was chosen for subsequent studies and was characterized for its surface area, surface chemistry properties, functional groups, porosity and surface morphology. The activated carbon was evaluated for its dye removal efficiency using methylene blue (MB) taking into consideration the following parameters; contact time, initial concentration of MB and adsorbent dosage. Maximum uptake (qmax) of MB by the adsorbent was determined based on goodness-of-fit according to the Langmuir, Freundlich and Redlich Peterson adsorption isotherm models. The adsorption equilibrium data was best fitted with the Langmuir adsorption isotherm with R2 of 0.969 and qmax at 288.34 mg/g. It can be concluded that adsorbent prepared using a 1:1 ratio has the highest dye removal capacity due to its high surface area (914.67 m2/g) and adsorption capacity at 288.34 mg/g. Thus, this study demonstrated the potential of using pineapple waste biomass as cheap and efficient raw materials to produce activated carbon for dye removal from wastewaters.