Effective kinetic modeling and phycoremediation of Cr(IV) ions from tannery effluent by using microalgae - Chlamydomonas moewusii, Auxenochlorella pyrenoidosa, Scenedesmus sp.

Chromium is a harmful heavy metal that is often found in tannery effluent. It is potentially toxic in nature and also acts as an anthropogenic source, so chromium ion is considered to be an environmental contaminant. The toxic effluents are generally treated in the process of remediation by using micro or macro-algae called "Phycoremediation" and it has shown effective cleanup approaches. The present study deals with the phycoremediation of chromium ion polluted effluent in Ambur tanneries. The isolated microalgae were collected from the estuary near the industrial site, which was observed for the preliminary metal tolerance activity then morphologically identified with the help of a compound microscope and they are named SMA1, SMA2, and SMA3. The taxonomical examination reveals that SMA1 is found to be 98.66% similar to Chlamydomonas moewusii, SMA2 was 99.24% similar to Scenedesmus sp., and SMA3 was 98.88% similar with Auxenochlorella pyrenoidosa. The identified microalgae were growing in the specific growth media BG11 and tannery effluent was supplemented along with the culture media to determine the growth rate, biomass production, and total protein content, which also regulates the potential bio-sorption and absorption rate of Cr(VI) ion. The activity of biosorption was seen to be 90% for C. moewusii (SMA1), 65% for Scenedesmus sp. (SMA2), and 80% for A. pyrenoidosa (SMA3), which showed the potential activity in phycoremediation process. Adsorption mechanism is studied by kinetic modeling of data experimentation which is bound with pseudo-first-order kinetics and pseudo-second-order kinetics; this mechanism exposed the adsorption capability of microalgae. The outcome of this study shows that the microalgae species are considered to be the most effective biosorbents for removing Cr(VI) ions from the tannery effluent.