Krishnani Kishore Kumar, Choudhary Khushboo, Boddu Veera Mallu, Moon Deok Hyun, Meng Xiaoguang
ICAR-Central Institute of Fisheries Education (Deemed University), Panch Marg, Off Yari Road, Versova, Andheri (W), Mumbai, 400061, India.
ICAR-National Institute of Abiotic Stress Management, Baramati, Pune, 413115, India.
Environ Sci Pollut Res Int. 2021 Feb 26. doi: 10.1007/s11356-021-12874-1.
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 (CCaO·HO) 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 bonded with carboxylate moieties. For both the bioadsorbents, the Pb, Cu, and Cd are biosorbed completely by ion exchange with Ca (89-94%) and Mg (7-12%), whereas Hg is biosorbed partially (57-66%) by ion exchange with Ca (38-42%) and Mg (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.
本文评估了从芒果（芒果属）和番石榴（番木瓜属）树皮衍生的生物吸附剂对有毒金属离子的生物吸附及其金属固定机制。发现芒果生物吸附剂的最大金属生物吸附容量按以下递增顺序排列（mg/g）：汞（16.24）＜铜（22.24）＜镉（25.86）＜铅（60.85）。番石榴生物吸附剂的最大金属生物吸附容量遵循类似顺序（mg/g）：汞（21.48）＜铜（30.36）＜镉（32.54）＜铅（70.25），但吸附容量略高。通过使用各种光谱、光谱学和显微镜方法研究生物吸附剂的表面性质和官能团，确定了使用生物吸附剂去除重金属的机制。基于使用X射线技术（XPS和XRD）对其表面性质的表征，在生物吸附剂中鉴定出了草酸钙（CaC₂O₄·H₂O），这促进了金属离子与与羧酸盐部分结合的钙进行离子交换。对于这两种生物吸附剂，铅、铜和镉通过与钙（89 - 94%）和镁（7 - 12%）的离子交换被完全生物吸附，而汞由于其他阳离子参与离子交换过程，通过与钙（38 - 42%）和镁（19 - 24%）的离子交换被部分生物吸附（57 - 66%）。生物吸附剂含有木质素，在酸性介质中木质素作为电子供体将六价铬还原为三价铬（分别为29.87和37.25 mg/g）。在较高pH值下，阴离子六价铬由于与带负电荷的羧基官能团的静电排斥而未被生物吸附剂吸附。
