Everything is interesting about the Atitlán-Gil 2017 publication.  The featured image is meant to illustrate the predicament that smokers experience. Toxins in the smoke are metabolized by the liver. The metabolites that are not so water soluble are secreted in the bile only to be reabsorbed. The natural zeolite Klinobind absorbs these toxins before they are reabsorbed. This is at least a working model to explain their results.  What makes this study different from other studies briefly mentioned in this post is that the participants were instructed to consume the clay before their first morning meal.
The natural zeolite Klinobind was supplied by Granding Internationa, SA de CV, Jiutepec, Morelos, Mexico. The zeolite was micronized by mechanical miconization and tribochemical and thermal activation. Tribology is the science of how materials behave under conditions of friction. Particle size as 1-11μM. The specific surface area was measured by the Branauer-ERmmett-Teller method was 2m2/g.
Vitamin E in the water soluble form of D-alpha tocopheryl acetate and maltodextrin were used as positive controls. Trolox is a water soluble analog of vitamin E, that like vitamin E, has the ability to scavenge reactive oxygen species. Malondialdehyde is a marker of oxidative stress. This image of malondialdehyde formation with a peroxyl radical reacting with an unsaturated fatty acid is from ResearchGate. Click on this link to view the publication.
Smokers were 19-60 years of age that had smoked 2-37 years and 8-29 cigarettes per day. Subjects with acute lung infections or other chronic illnesses were excluded. Also excluded were subjects on anti-oxidant drugs and/or pharmaceuticals. There were 29 smokers in the ZAM and vitE groups and only 27 in the maltodextrin group. ZAM subjects received 5.4g per day, vitamin E 400 mg D-α-tocophenyl acetate, and 250 maltodextrin. Subjects took the study compounds in the morning before consumption of food for 30 days. As a general note, they probably had pancreatic and gall bladder emptying if this material had sufficient bulk to activate the enteric nervous system of the fundus.
In spite of likely typos in table 1 and Figure 1, it is not surprising that vitamin E supplementation will almost double Trolox units. What is truly remarkable is that micronized an activated zeolite has a simila effect. Catalase, the heme iron containing enzyme, activity was increased by Vitamin E and ZAM. 
Less serum H2O2 in the vitamin E treatment group goes along with vitamin E’s role as well as increased catalase activity. Both vitamin E and ZAM decrease levels of the MDA byproduct of lipid peroxidation.  Consuming ZAM on an empty stomach long after the evening meal has (probably) passed into the colon suggests binding of liver secretions via the gall bladder before those compounds can reenter the enterohepatic circulation. These images on gall bladder secretion are from mhealthknowledge.org. According to this link bile acids are responsible for solubilization of fats into micelles so the fats may be digested by pancreatic lipases. Gall bladder secretions may also contain cholesterol, hemoglobin breakdown product bilirubin, drugs, and heavy metals. This site reiterates the role of the liver in degrading and and adding hydrophilic conjugates to toxins so that they are more water soluble for excretion in the urine. What seems to be implied that the not so water soluble conjugates are excreted in the bile.
What heavy metals and not so water soluble cigarette toxins get secreted into the bile only to reenter the circulation? These images of urobilinogen suggest the same may be true for cigarette smoke toxins. Does ZAM absorb these heavy metals and/or toxins?
Do zeolites prevent (re) absorption of heavy metals?
Croatian clinical trials and chronic consumption. Kraljevic Paveli and coauthors published a summary of three zeolite chlinical trials in Croatia 
“Explorative Clinical Trial on Healthy Subjects (Mineral Metabolism and Selected Blood Parameters These subjects took PMA-zeolite for28 days. Two groups of volunteers were involved : a naïve group were new PMA-zeolite users.” They took 6g PMA-Z in the study. The mean age of these 7 male and female volunteers was 45. The chronic group consisted of 8 volunteers with a mean age of 56 years among male and female participants. All of these 8 volunteers had used 6 g PMA-zeolite or more per day for 6 months and to 8 years before the start of the trial. Many serum heavy metals were examined with inconclusive results, in my opinion.  This report became too much not knowing the heavy metal content of the those in the Croat Republic and when they consumed the zeolite. 
Clinoptilolite zeolite spiked with lead
42 participants were studied in the fasting state. 
- placebo drinking solution (2 * 100 ml water),
- 2.0 g G-PUR suspended in 100 ml water
- 2.0 g G-PUR suspended in 100 ml water each, together with 250 ml still mineral water containing 2.5 μg of 204Pb, the then G-PUR as a chaser.
This stock solution was diluted to a final 204Pb concentration of 10.0 µg/l. The clinoptilolite prevented lead absorption. This study unfortunately did not address the enterohepatic nuance of lead absorption.
And chemothrapy related neuropathy
This study took place in Italy.… a part of the world in which G-PUR consumption seems almost a fad. The chemotherapy agent in question was oxaliplatin, a platinum based chelate. The treatment group received 6 g/day PMA-zeolite (Multizeo Med, Goedersdorf, Austria) in two daily doses of 3 g. When and how was not mentioned in this paper. The placebo group received 6 g/day of placebo (microcrystalline cellulose as it was used in another randomized, double-blinded, placebo-controlled trial.  The PMA-zeolite seemed to improve toxicology parameters.  The frustrating thing from a mechanistic point of view is that Pt levels in the blood, feces, and urine were not measured. Pt uses the Cu+ export ATP7B 
ATP7B is expressed in the liver and a means of eliminating excess Cu from the body and into the feces. Naturally, the Cu can be reabsorbed by Cu transporter Ctr1.
- Atitlán-Gil A, Bretón-de la Loza MM, Jiménez-Ortega JC, Belefant-Miller H, Betanzos-Cabrera G. A(2017) Activated and Micronized Zeolite in the Modulation of Cellular Oxidative Stress in Mexican Smokers: A Randomized Clinical Trial. Rev Invest Clin. 2017 May-Jun;69(3):146-151. PMC free article
- Kraljević Pavelić S, Saftić Martinović L, Simović Medica J, Žuvić M, Perdija Ž, Krpan D, Eisenwagen S, Orct T, Pavelić K. Clinical Evaluation of a Defined Zeolite-Clinoptilolite Supplementation Effect on the Selected Blood Parameters of Patients. Front Med (Lausanne). 2022 May 27;9:851782. free article
- Samekova K, Firbas C, Irrgeher J, Opper C, Prohaska T, Retzmann A, Tschegg C, Meisslitzer C, Tchaikovsky A, Gouya G, Freissmuth M, Wolzt M. Concomitant oral intake of purified clinoptilolite tuff (G-PUR) reduces enteral lead uptake in healthy humans. Sci Rep. 2021 Jul 20;11(1):14796. PMC free article
- Vitale MG, Barbato C, Crispo A, Habetswallner F, Martino BM, Riccardi F, Maione A, Eisenwagen S, Vitale G, Cartenì G. ZeOxaNMulti Trial: A Randomized, Double-Blinded, Placebo-Controlled Trial of Oral PMA-zeolite to prevent Chemotherapy-Induced Side Effects, in particular, Peripheral Neuropathy. Molecules. 2020 May 13;25(10):2297. PMC free article
- Li YQ, Yin JY, Liu ZQ, Li XP. Copper efflux transporters ATP7A and ATP7B: Novel biomarkers for platinum drug resistance and targets for therapy. IUBMB Life. 2018 Mar;70(3):183-191. PMC free article