Tight sorption of arsenic, cadmium, mercury, and lead by edible activated carbon and acid-processed montmorillonite clay
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RESEARCH ARTICLE
Tight sorption of arsenic, cadmium, mercury, and lead by edible activated carbon and acid-processed montmorillonite clay Meichen Wang 1 & Gopal Bera 2 & Kusumica Mitra 2 & Terry L. Wade 2 & Anthony H. Knap 2 & Timothy D. Phillips 1 Received: 9 May 2020 / Accepted: 21 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Heavy metal exposure in humans and animals commonly occurs through the consumption of metal-contaminated drinking water and food. Although many studies have focused on the remediation of metals by purification of water using sorbents, limited therapeutic sorbent strategies have been developed to minimize human and animal exposures to contaminated water and food. To address this need, a medical grade activated carbon (MAC) and an acid processed montmorillonite clay (APM) were characterized for their ability to bind heavy metals and mixtures. Results of screening and adsorption/desorption isotherms showed that binding plots for arsenic, cadmium, and mercury sorption on surfaces of MAC (and lead on APM) fit the Langmuir model. The highest binding percentage, capacity, and affinity were shown in a simulated stomach model, and the lowest percentage desorption (< 18%) was shown in a simulated intestine model. The safety and protective ability of MAC and APM were confirmed in a living organism (Hydra vulgaris) where 0.1% MAC significantly protected the hydra against As, Cd, Hg, and a mixture of metals by 30–70%. In other studies, APM showed significant reduction (75%) of Pd toxicity, compared with MAC and heat-collapsed APM, suggesting that the interlayer of APM was important for Pb sorption. This is the first report showing that edible sorbents can bind mixtures of heavy metals in a simulated gastrointestinal tract and prevent their toxicity in a living organism. Keywords Heavy metals . Activated carbon . Adsorption/desorption isotherms . Hydra . Montmorillonite clay . Acid activation
Introduction Heavy metal contaminants cause important problems due to their mobility in the aqueous ecosystem, their accumulation in the environment and food chain, their hazards to higher life forms, and their non-biodegradable nature (Lasheen et al. 2012; Mishra 2014). Diet is the main route of exposure to metals and significant health risks to humans and animals have been strongly associated with metal exposure. Arsenic, cadmium, lead, and mercury (U.S Food and Drug
Responsible Editor: Tito Roberto Cadaval Jr * Timothy D. Phillips [email protected] 1
Veterinary Integrative Biosciences Department, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, TX 77843, USA
2
Geochemical & Environmental Research Group, Texas A&M University, College Station, TX 77845, USA
Administration 2019, 2020) are at the top of the list and have been prioritized as the most hazardous metals by the Agency for Toxic Substances and Disease Registry (ATSDR 2019). Arsenic (As) is commonly found in groundwater from natural and industrial processes. It
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