Heavy metals biosorption mechanism of partially delignified products derived from mango (Magnifera indica) and guava (Psidium guiag) barks

Authors: KRISHNANI, KISHORE - Indian Council Of Agricultural Research (ICAR); CHOUDHARY, KHUSHBOO - Indian Council Of Agricultural Research (ICAR); Boddu, Veera; MOON, DEOK - Chosun University; MENG, XIAOGUANG - Stevens Institute Of Technology

Submitted to: Environmental Science and Pollution Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2021
Publication Date: 2/26/2021
Citation: Krishnani, K.K., Choudhary, K., Boddu, V.M., Moon, D.H., Meng, X. 2021. Heavy metals biosorption mechanism of partially delignified products derived from mango (Magnifera indica) and guava (Psidium guiag) barks. Environmental Science and Pollution Research. 28:32891-32904. https://doi.org/10.1007/s11356-021-12874-1.
DOI: https://doi.org/10.1007/s11356-021-12874-1

Interpretive Summary: Toxic metals in water is a major health concern. Toxic metals such as mercury and lead bioaccumulate in fish and other aquatic organisms which can then be transferred to people upon consumption. This research evaluates the use of the barks of mango and guava trees for removing mercury, copper, cadmium, and lead metal ions from water. The barks are first subjected to a simple water (high pH) treatment to activate them. The treated bark is then dried and ground and evaluated in the laboratory for their ability to capture toxic metals. The methods developed with these barks can be extended to other woods. This research will eventually develop a low-cost process for reducing metals in aquaculture ponds, groundwater, and other drinking water resources.

Technical Abstract: 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 (C2CaO4.H2O) 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 Ca2+ bonded with carboxylate moieties. For both the bioadsorbents, the Pb2+, Cu2+, and Cd2+ are biosorbed completely by ion exchange with Ca2+ (89-94%) and Mg2+ (7-12%), whereas Hg2+ is biosorbed partially (57-66%) by ion exchange with Ca2+ (38-42%) and Mg2+ (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.