Biomass of digested sludge and resting sludge can be easily applied as a cheap bio-adsorbent for heavy metal ions such as Pb2+, Cu2+ and Cd2+. Langmuir model was found to fit the experimental adsorption and desorption data of the heavy metal on to the biomass of sludge. That has the competition uptake between the difference metal with another when the adsorption system has the di-metal, and tri-metal combination. The maximal adsorption capacity of resting sludge was 0.517 mM Pb2+/g; 0.552 mM Cu2+/g; 0.389 mM Cd2+/g, and the maximal adsorption capacity of the digested sludge was 0.478 mM Pb2+/g, 0.43 mM Cu2+/g and 0.549 mM Cd2+/g. In the absorption system, it was found that, di-metal combine such as (Cu2+ - Cd2+), (Pb2+ Cd2+), and (Cu2+ - Pb2+), the metal uptake Cu2+ ≈ 3Cd2+, Pb2+ > 3Cd2+, and Cu2+ ≈ Pb2+ respectively. When tri-metal Cu2+ - Cd2+ - Pb2+ combines the number of complex formation varies in the following order: Pb2+ > Cu2+ > Cd2+. Extracellular polymeric substances (EPS) were extracted by sonication method. Humic substances were greater than protein and polysaccharide for digested sludge, for resting sludge the protein is greater than humic. The ratio protein/polysaccharide varies from 1.25 to 2.7, this ratio is highest for resting sludge. Affinity absorption of Cu2+ and Pb2+ was higher than Cd2+, that have the competition metal uptake with functional groups such as hydroxyl, carbonyl, amide on the biomass surface of the sludge.Keywords: Activated sludge; Bio-sorption; Cd2+; Cu2+; Pb2+Tom TatHAP THU CAC KIM LOAI NANG Pb(II), Cu(II) va Cd(II) TREN SINH KHOI KHAC NHAU CUA BUN HOAT TINHSinh khoi cua bun hoat tinh va bun duoc xu ly la chat hap thu sinh hoc re tien doi voi cac kim loai nang nhu Pb2+, Cu2+ and Cd2+. Phuong trinh dong hoc Langmuir mo ta qua trinh hap thu va giai hap thu cac kim loai nang doi voi chat hap thu la sinh khoi cua bun rat phu hop. Trong he da nguyen to co su hap thu canh tranh giua cac nguyen to voi nhau. Hap dung cuc dai cua bun hoat tinh tren 1 gram sinh khoi kho tuong ung 0,517 mM Pb2+; 0,552 mM Cu2+; 0,389 mM Cd2+; trong khi do hap dung cuc dai cua bun hoat tinh da duoc xu ly tuong ung 0,478 mM Pb2+, 0,43 mM Cu2+ va 0,549 mM Cd2+. Ket qua nghien cuu cho thay, trong he hap phu co 2 cau tu (Cu2+ - Cd2+), (Pb2+ - Cd2+), va (Cu2+ - Pb2+) thi trat tu canh tranh tuong ung Cu2+ ≈ 3Cd2+, Pb2+ > 3Cd2+, and Cu2+ ≈ Pb2+. Trong khi do doi voi he hap phu co 3 cau tu Cu2+ - Cd2+ - Pb2+ thi trat tu canh tranh la Pb2+ > Cu2+ > Cd2+.Extracellular polymeric substances (EPS) duoc chiet bang phuong phap sieu am. Ket qua nghien cuu cho thay doi voi bun da duoc xu ly hop phan cua humic nhieu hon protein va polysaccharide, nguoc lai doi voi bun hoat tinh co protein cao hon humic. Ty le PN/PS thay doi tu 1,25 den 2,7: ty le nay cao nhat doi bun hoat tinh. Ai luc hap phu Cu2+ va Pb2+ boi bun hoat tinh cao hon Cd2+ la do co su canh tranh hap thu cua cac ion kim loai doi voi cac nhom chuc hydroxyl, carbonyl, amide tren be mat sinh khoi bun hoat tinh.Tu khoa: Bun hoat tinh; Cd2+; Cu2+; Pb2+; sinh hap phu