Adsorption and Release Characteristics of Purified and Non-Purified Clinoptilolite Tuffs towards Health-Relevant Heavy Metals

Abstract

The occurrence of health-relevant contaminants in water has become a severe global problem. For treating heavy-metal-polluted water, the use of zeolite materials has been extended over the last decades, due to their excellent features of high ion exchange capacity and absorbency. The aim of this study was to assess the effect of heavy metal uptake of one purified (PCT) and two non-purified clinoptilolite tuffs (NPCT1 and NPCT2) in aqueous solutions on monovalent ions Ni+, Cd+, Cs+, Ba+, Tl+, and Pb+. Experiments were furthermore carried out in artificial gastric and intestinal fluids to mimic human digestion and compare removal efficiencies of the adsorbent materials as well as release characteristics in synthetic gastric (SGF) and intestinal fluids (SIF). Batch experiments show low sorption capacities for Ni+ and Cd+ for all studied materials; highest affinities were found for Ba+ (99–100%), Pb+ (98–100%), Cs+ (97–98%), and Tl+ (96%), depending on the experimental setup for the PCT. For the adsorption experiments with SGF, highest adsorption was observed for the PCT for Pb+, with an uptake of 99% of the lead content. During artificial digestion, it was proven that the PCT did not release Ba+ cations into solution, whereas 13,574 ng·g−1 and 4839 ng·g−1 of Ba+ were measured in the solutions with NPCT1 and NPCT2, respectively. It was demonstrated that the purified clinoptilolite tuff is most effective in remediating heavy-metal-polluted water, particularly during artificial digestion (99% of Pb+, 95% of Tl+, 93% of Ba+). In addition, it was shown that the released amount of bound heavy metal ions (e.g., barium) from the non-purified clinoptilolite tuffs into the intestinal fluids was significantly higher compared to the purified product.

Purified Clinoptilolite-Tuff as an Efficient Sorbent for Gluten Derived from Food

“…For all experiments presented in this study, a special purified clinoptilolite-tuff (PCT), intensively tested and approved for prolonged human application [14,15,19], was used. Due to a patented purification process, PCT is free of toxic elements and safe for supplemental oral intake [13].…”

“…Purified clinoptilolite-tuff can sorb different kinds of substances. In a clinical trial, it was described as a safe and highly effective binder for lead in drinking water [14] and as sorbent for health-relevant heavy metals in vitro [15]. Therefore, the binding of prolamins from food seems to be reasonable.…”

Binding and inactivation of human coronaviruses, including SARS-CoV-2, onto purified clinoptilolite-tuff

“…The final purified product has been evaluated by independent laboratories and trials conforming the safety requirements for human consumption and efficacy. In the U.S., PCT is marketed as G-PUR®, which has been successfully applied in different therapeutic indications 22 , 23 , 39 .…”

Sorption of Natural Siderophores onto Clinoptilolite-Tuff and Its Controlled-Release Characteristics

“…Furthermore, the authors in the aforementioned studies [12,21] described cation-like sorption behavior for the organic siderophore molecules. Since clinoptilolite has shown efficient uptake of metal cations in previous studies [24,25], there is reason to deduce that clinoptilolite is an appropriate controlled-release carrier substrate for siderophores. Clinoptilolite, the major mineral constituent of clinoptilolite-tuff, is a heulandite-type zeolite mineral, a hydrated aluminosilicate that shows a unique structure due to its framework of linked SiO 4 and AlO 4 tetrahedra [26].…”