Removal of Cr (VI) from Aqueous Solution using Orange Peel-based Biosorbents

Background: Now-a-days, adsorption has been recognized as an effective method to remove heavy metals ions in water sources. Objectives: This work is focused on studying removal of chromium (VI) from aqueous solution by orange peel-based adsorbents (OP, OPAC, OP-CaCl₂ and OP-Chitosan). Effects of pH and adsorbent dosage on the adsorption of Cr (VI) were evaluated in order to determine suitable conditions for carrying out adsorption process. Methods/ Analysis: OP-CaCl₂ and OPAC biosorbents were obtained by chemical modification using CaCl₂ and H₃PO₄ acid solution, respectively, while OP-Chitosan was synthetized in acetic acid solution. FT-IR analysis was performed to OP and OP-Chitosan materials. The pH of heavy metal ions solutions was adjusted to3, 4 and 5 and adsorbent dosage was varied in 2, 4 and 6 g/L. Batch experiments were carried out in a magnetic stirrer plate at 30°C using 100 ppm Cr (VI) ions solution. Experimental data of equilibrium were used to calculate adsorption isotherms. Findings: The adsorption of Cr (VI) was found to be maximum for OPAC biosorbent and its highest removal yield (66.8%) was achieved at pH 3 and dosage of 6 g/L. Application of the Langmuir isotherm to OP biosorbent yielded a maximum adsorption capacity of 911.21 mmol/g and the data for OPAC and OP-Chitosan obeyed Freundlich isotherm with KL of 0.25 mmol/g and 8.17 mg/g, respectively. The heterogeneity factor (1/n) indicated that OPAC obeys to cooperative adsorption and OP-Chitosan to chemisorption. Application/Improvement: Compared to the various other adsorbents reported in the literature, the orange peel-based adsorbents in this study show very good promise for practical applicability.