Metals bioaccumulation mechanism in neem bark

Authors: KRISHNANI, KISHORE - National Institute Of Abiotic Stress Management; Boddu, Veera; MOON, DEOK - Chosun University; GHADGE, S - National Institute Of Abiotic Stress Management; SARKAR, BIPLAB - National Institute Of Abiotic Stress Management; BRAHMANE, M - National Institute Of Abiotic Stress Management; CHOUDHARY, K - Directorate Of Weed Science Research; KATHIRAVAN, V - The Madura College; MENG, XIAOGUANG - Stevens Institute Of Technology

Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2015
Publication Date: 7/21/2015
Citation: Krishnani, K.K., Boddu, V.M., Moon, D.H., Ghadge, S.V., Sarkar, B., Brahmane, M.P., Choudhary, K., Kathiravan, V., Meng, X. 2015. Metals bioaccumulation mechanism in neem bark. Bulletin of Environmental Contamination and Toxicology. 95(3):414-419.

Interpretive Summary: Toxic metals such as arsenic, lead, chromium, mercury, and cadmium are present in drinking water resources as a result of both natural and anthropogenic activities. In natural waters, and thus in drinking water, arsenic found in several chemical forms. Arsenic dissolved in water is acutely toxic and can lead to a number of health problems. Usually arsenic is built up in the body through drinking water causes increased risks of cancer in the skin, lungs, liver, kidney, and bladder. Similarly lead and chromium are also very toxic to human and animal health. The US Environmental Protection Agency in 2001 has adopted a new standard for arsenic in drinking water at 10 ppb, replacing the old standard of 50 ppb. Drinking water sources (e.g. ground water) in the rural areas need simple and cost effective way of treating their raw source water. Agriculture wastes such as corn cobs, soybean hulls and other plant materials may provide a cost effective preliminary treatment options for reducing toxic metals and other organic toxins. A bed of carefully selected plant material may provide a preliminary water treatment option to reduce overall water treatment costs as a result of reduced load on the ion-exchangers (salt based water hardness removal) and under the sink reverse osmosis units. The research presented in this paper describes evaluation of a plant (neem) bark material as an adsorbent material for several toxic metals. This study provides preliminary metals bioaccumulation properties of agricultural plant wastes, and potential drinking water and surface treatment options.

Technical Abstract: The aim of this work was to define the bioaccumulation mechanism of metals onto the non-living biomaterial prepared from an extensively available plant bark biomass of neem (Azadirachta indica). Based on maximum ultimate fixation capacities (mmol/g) of the product, metals ions could be arranged as Hg(2+) < Cd(2+) < Pb(2+) ' Cu(2+). Surface properties of the biomaterial were characterized by X-ray photoelectron spectroscopy and X-ray diffraction techniques for their sorption mechanism. Whewellite (C2CaO4•H2O) was identified in the biomaterial, which indicated that calcium ions are electrovalently bonded with carboxylate ions facilitating the ion exchange mechanism with metal ions. Bioaccumulation of metal ions was also studied by Fourier transform infrared spectroscopy, which indicated the presence of functional groups implicated in adsorbing metal ions. Biomaterial did not adsorb anionic As(III), As(V) and Cr(VI), because of their electrostatic repulsion with carboxylic functional groups. Neem bark can be used as bioindicators, bioaccumulators and biomonitors while determining environmental pressures. Metal bioaccumulative properties and structural investigation of plant bark has potential in providing quantitative information on the metal contamination in the surrounding environment.