Dissertation (MSc. Chemistry)This study was conducted to investigate the effectiveness of natural and synthetic materials as adsorbents for hard water treatment by using EDTA titrimetric method. Natural adsorbent prepared from cactus and synthetic adsorbent prepared by grafting potato starch and the study conducted on water samples collected from Nzuguni, Ng’ohong’hona, Kisasa and Swaswa in Dodoma municipality. The results revealed that the concentration of hardness decreased as the dose of (Cactus Materials Adsorbents) CMA and (Grafted Materials Adsorbents) GMA increased. The initial hardness before treatment was 547mg/L. with 0.5 g of CMA and GMA the hardness reduced to 268.7mg/L and 246.5mg/L respectively. The effective dose for CMA was 3.5 g with reduced hardness of 105.5 mg/L and for GMA was 2.5g with hardness of 189.1mg/L. The maximum efficiency of hardness removal for CMA was 80.7% and for GMA was 68.4%.The data generated showed that the adsorption process fitted Langmuir type II &IV isothermal model for CMA and GMA respectively with its coefficient of correlation value was R2 =0.99504 and R2 =0.99936 for the CMA and GMA respectively, The data fitted for pseudo second-order kinetic model with coefficient correlation value of ≥ 0.9 compare with a pseudo first-order kinetic model with coefficient correlation value of ≤ 0.7.Also the regeneration shows that the adsorbents materials have ability to adsorb again hardness . From this study CMA have shown higher efficiency in hardness removal compared to GMA, hence CMA is highly recommended for the hardness removal purposes.