The present invention provides a method for the preparation of multi-nutrient potassic fertilizer, by recovering potassium from sugarcane molasses based alcohol distillery effluent (commonly known as ‘spent wash’). The process involves pre-treatment of spent wash to clarify the aqueous phase and utilization of the treated spent wash in production of potassic fertilizer. The present invention enables utilisation of spent wash for recovery of value-added product (viz., potash fertiliser of >99% purity) and improves ease of ‘Zero Liquid Discharge’ compliance by subjecting the relatively benign process effluent to industrially practiced techniques for water recovery and salt reclamation.