A practical review of the performance of organic and inorganic adsorbents for the treatment of contaminated waters

A wide range of materials known for their adsorption properties have the potential for being used for the removal of trace substances from drinking and wastewaters. These include physically and chemically activated carbons, surface modified carbons, non-porous resins with ion exchange capacities, inorganic microporous solids like zeolites and clays, and mixed organic-inorganic materials like bone chars. The adsorption capacity exhibited by each material relates primarily to its textural and chemical properties. Other factors, however, such as apparent density, regeneration potential and cost, need to be taken into consideration when selecting one adsorbent over another. A comparative investigation of 18 solids and their capacity to remove organics and metals from natural waters and solutions reconstituted to simulate the conditions in natural waters is presented. The experiments were carried out using batch and small-scale column adsorption tests. In general, zeolites and ion exchange resins exhibited limited capacities to remove organic matter from solution but were highly effective with metallic species like manganese and aluminium. Activated carbons adsorbed organic matter very efficiently, with results showing a correlation between adsorption capacity and surface area (up to 1791 m(2) g(-1)). Metal removal was highly variable and was enhanced in activated carbons subjected to acid washing. Owing to its mixed organic/inorganic nature, and despite its poorly developed micropore structure, bone char exhibited a strong adsorption capacity for both organic and metal species. The high apparent density of this material (0.763 g cm(-3)) meant that its performance was greatly improved when tests were conducted on the basis of volume, matching and surpassing the performance of the best carbons. The possibility of using mixtures of complementary adsorbents for the removal of organic and inorganic species from solution was also successfully evaluated in this work. (c) 2006 Society of Chemical Industry.