Abstract:The idea of using microorganisms, especially microalgae, as biosorbents of heavy metals deserves particular attention due to their natural biosorbent properties and the relatively simple and inexpensive methods of obtaining their biomass. The cosmopolitan microscopic green alga of the genus Pseudopediastrum is an example of an organism with the desired biosorption properties. The aim of the study was to assess the potential use the dry biomass of Ps. boryanum var. longicorne in the process of biosorption of chromium(VI) (Cr(VI)) ions from aqueous solutions. Biomass of microalgae was cultivated in the photobioreactor conditions (L-S2T2 medium, light intensity of 4000 lx, photoperiod 12L:12D). The biomass obtained was used for the biosorption of Cr(VI) ions from aqueous solution. The effect of pH (2-6), biosorbent concentration (0.5-2 g/L) and initial chromium concentration (10-100 mg/L) was examined. The highest removal of Cr(VI) ions (70%) was observed at pH 2, initial chromium concentration of 10 mg/L and a biomass concentration of 2 g/L. At this chromium concentration, the sorption capacity of the microalga was the lowest. The results indicated that the biomass of the Ps. boryanum is suitable for the development of efficient biosorbent for the removal of Cr(VI) from wastewater.

The present results are the effect of bioprospecting of an appropriate medium, which could optimize the quality and quantity of the microalga Pseudopiediastrum boryanum var. longicorne Reinsch biomass cultured in a laboratory photobioreactor for biosorption purposes. Four liquid media commonly used for cultivation of green algae of the genus Pediastrum were compared, including Knop's, Waris-H, Chu's and L-S2T2 media, which differed with respect to the composition and concentration of nutrients. A number of the parameters characterizing biomass growth, namely dry weight, optical density, chlorophyll a concentration, as well as morphological parameters characterizing the condition of the alga and its surface area indicating the potential sorption capacity (population structure, cell number, coenobium size and marginal cell size), showed a significant impact of culture medium on the growth of the microalga. The most productive culture was found in the L-S2T2 medium containing organic substances in the form of peat and soil extracts, which could be crucial for biomass production and the area of potential sorption capacity. P < 0.001), L-S2T2 and Chu's ( c P < 0.05), L-S2T2 and Waris-H ( b P < 0.05, bb P < 0.01, bbb P < 0.001), Chu's and Knop's ( d P < 0.05, dd P < 0.01).

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