Adsorption Technology for Removal of Toxic Pollutants

Abstract

Metals present in natural waters are nondegradable, unlike organic compounds. These metals lead to somatic cell mutation that causes increased cancers amongst children throughout the world. The existing remediation methodologies for removal of such toxic metals are oxidation, coagulation and flocculation, precipitation, ion exchange, membrane filtration, ozone oxidation and bioremediation. Most of the methods involve production of high metal-contaminated sludge and high maintenance cost or the use of a relatively expensive mineral matrix that offset the performance and efficiency advantages. Adsorption has largely emerged as significant technology for removal of toxic metals. The review of over 240 published studies (1982–2016) shows an exhaustive list of adsorbents in the literature, including chitosan, fly ash, used tyre rubber, wood char, rice husk, aluminosilicates, etc. This review shows that the modification of most of the adsorbents offers outstanding performances to solve heavy metal related pollution issues. The removal of toxic metals using natural adsorbents is economical and environment friendly. Treated clay shows increased removal of metal ions under the same conditions compared to the untreated clay minerals due to increased surface area. One of the best adsorption capacities reported for As is 95% from 1 mg/L using hybrid adsorbents, 98% of Sb from 0.05 mg/L using hydroxyapatite and 97% of Cd from 10 mg/L using A. rubescens biomass.