Methylene blue removal by agricultural wastes from Annona muricata and Treculia africana seeds

Industrial wastewater discharge is of great environmental concern worldwide and is necessitated by human activities where dyes are used as raw materials and untreated or poorly treated effluents discharged into nearby environments. Adsorption being one of the processes by which dye polluted effluents are efficiently removed, thus the search for low-cost adsorbents has necessitated this study. Annona muricata seed (AMS) and Treculia africana seed hull (TASH) are agricultural waste materials proposed as alternatives for the removal of methylene blue (MB) from aqueous solutions. The effects of agitation time, initial concentration, biosorbent dosage, initial solution pH, and temperature gave good results for the biosorption of MB onto AMS and TASH. Chemisorption and physisorption mechanisms are proposed from kinetic and equilibrium studies. Scanning electron microscopy (SEM) and infrared spectroscopy (FTIR) reveal effective biosorption processes. Thermodynamic parameters calculated reveal spontaneous and endothermic biosorption of MB onto AMS and TASH. Thermogravimetric analysis results reveal that AMS and TASH are thermally stable for biosorption use at ambient conditions. AMS and TASH are used as alternative biosorbents for MB from aqueous solutions and are encouraged considering they are easily available, economic, and efficient, having removed over 95% of MB at pH of 6 and 303 K. Results suggest that AMS and TASH are effective alternative biosorbents for methylene blue removal from aqueous solutions.