In our clay nutrient, zeolite nutrient and biochar nutrient sorption studies, we receive suspension of turbid, faint and black colour nutrient solution respectively. Although high 15000 rpm centrifuge for more than 30 min, after 2 time filtration, we unable to separate fine clay, zeolite and char from solution. However, it interferes in colorimetric estimation and other analysis. Alum is good coagulant. We used a pinch alum for separation , received clear solution . My doubt is whether alum adsorb nutrient forms (N,P,K and micronutrients). kindly provide your inputs which will help me for finalizing sorption methodology.