The study investigated the removal of divalent manganese (Mn2+) cations using watermelon rinds, as a low cost adsorbent, in a batch-type adsorption system under different ranges of the most important operating conditions affecting the adsorption process, which included pH, contact time, initial concentration of divalent manganese ions (Mn2+), agitation rate, temperature, and adsorbent dosage. The operating factor values varied between 1-10, 5-180 minutes, 1-40 ppm, 100-500 rpm, 25-50°C, and 0.5-7 g, respectively. The results obtained indicated that a dose of 6.5 g of Iraqi virgin watermelon rinds successfully treated solutions contaminated with divalent manganese (Mn2+) cations by 81.4% in 150 minutes, at the highest temperature, with an agitation speed of 400 rpm, and a pH of 8.