| Autor: |
Krishnani KK; ICAR-Central Institute of Fisheries Education (Deemed University), Panch Marg, Off Yari Road, Versova, Andheri (W), Mumbai, 400061, India. krishnanik@hotmail.com., Choudhary K; ICAR-National Institute of Abiotic Stress Management, Baramati, Pune, 413115, India., Boddu VM; Plant Polymer Research Unit (PPL), National Center for Agriculture Utilization Research (NCAUR), Agricultural Research Service, US Department of Agriculture, ARS/USDA, 1815N University St, Peoria, IL, 61604, USA., Moon DH; Department of Environmental Engineering, Chosun University, Gwangju, 61452, Republic of Korea., Meng X; CEE, Stevens Institute of Technology, Hoboken, NJ, 07030, USA. |
| Abstrakt: |
This paper evaluates the biosorption of toxic metal ions onto the bioadsorbents derived from mango (Mangifera indica) and guava (Psidium guiag) barks and their metal fixation mechanisms. Maximum metal biosorption capacities of the mango bioadsorbent were found in the following increasing order (mg/g): Hg (16.24) < Cu (22.24) < Cd (25.86) < Pb (60.85). Maximum metal biosorption capacities of guava bioadsorbent follow similar order (mg/g): Hg (21.48) < Cu (30.36) < Cd (32.54) < Pb (70.25), but with slightly higher adsorption capacities. The removal mechanisms of heavy metals using bioadsorbents have been ascertained by studying their surface properties and functional groups using various spectrometric, spectroscopic, and microscopic methods. Whewellite (C 2 CaO 4 ·H 2 O) has been identified in bioadsorbents based on the characterization of their surface properties using X-ray techniques (XPS and XRD), facilitating the ion exchange of metal ions with Ca 2+ bonded with carboxylate moieties. For both the bioadsorbents, the Pb 2+ , Cu 2+ , and Cd 2+ are biosorbed completely by ion exchange with Ca 2+ (89-94%) and Mg 2+ (7-12%), whereas Hg 2+ is biosorbed partially (57-66%) by ion exchange with Ca 2+ (38-42%) and Mg 2+ (19-24%) due to involvement of other cations in the ion exchange processes. Bioadsorbents contain lignin which act as electron donor and reduced Cr(VI) into Cr(III) (29.87 and 37.25 mg/g) in acidic medium. Anionic Cr(VI) was not adsorbed onto bioadsorbents at higher pH due to their electrostatic repulsion with negatively charged carboxylic functional groups. |
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