## Materials and Methods
### In Vitro Isothermal Adsorption  
The toxin solutions of PCP, 2,4,6-TCP and diazinon were individually prepared by dissolving pure crystals into distilled water at pH 2 to simulate stomach pH. Final solutions were equal to 4 ppm (\(\mu\)g/mL) PCP, 6 ppm 2,4,6-TCP, and 10 ppm diazinon. Paraquat was dissolved into distilled water at pH 7 (since its structure is unaffected by pH) with a final solution equal to 5 ppm paraquat. Other toxin solutions were dissolved into the individual mobile phase (based on the methods of detection) with 12.5 ppm lindane (acetonitrile:water, 50:50), 20 ppm linuron (acetonitrile:water, 65:35) and 20 ppm trifurlain (acetonitrile:water, 70:30). The maximum concentrations were set based on the octanol-water partitioning coefficients (K\({}_{\text{ow}}\)) so that precipitation was not a factor, and the optimal ratio of toxin/clay to reach saturation (equilibrium) on isotherm plots was investigated. Then a concentration of 0.002% of sorbent was exposed to an increasing concentration gradient (5-100%) of toxin solution. In these studies, controls consisted of untreated solution, toxin solution without sorbent and sorbent suspension without toxin. The control and test groups were capped and agitated at 1000 rpm for 2 h at ambient temperature (24 \({}^{\circ}\)C) using an IKA(r) electric shaker (VIBRAX VXR basic, Werke, Germany). This time was based on preliminary data suggesting that equilibrium of the surface interaction was reached within 30 min. All samples were then centrifuged at 2000 \(g\) for 20 min to separate the clay/toxin complex from solution and were detected by either ultraviolet (UV)/visible scanning spectrophotometry, HPLC, or liquid chromatography/tandem mass spectrometry LC/MS/MS. A SHIMADZU UV/visible scanning spectrophotometry (UV-1800, SHIMADZU Corporation, Kyoto, Japan) was used to analyze PCP and 2,4,6-TCP concentrations in the resulting supernatants for each sample [32; 33; 34]. The concentrations were determined in supernatant samples that were placed in a quartz cuvette versus a blank and scanned through the UV region of the electromagnetic spectrum (between 200 and 800 nm) to establish the wavelength for maximal absorption of PCP and 2,4,6 TCP. The concentrations of toxins were determined at 210 nm (PCP) and 294 nm (2,4,6-TCP). HPLC (Milford, MA, USA) with a Phenomener(r) luna 5u C18 column (250 \(\times\) 4.6 mm) kept at an ambient temperature, was used to measure the absorption of lindane and linuron [35; 36]. Lindane was separated by 50% acetonitrile and 50% water as the mobile phase at 2.0 mL/min flow rate and 10 \(\mu\)L injection volume. Free lindane concentration in the supernatant was detected by a UV detector at 254 nm wavelength [35]. For linuron, separation was achieved by a mobile phase of 65% acetonitrile and 35% water, a flow rate at 1.0 mL/min, 20 \(\mu\)L injection volume and UV absorption at a 210 nm wavelength [36]. Breeze(r) software was used to control the HPLC system and collect data. HPLC with a SUPELCOSIL LC-18 column (15 \(\times\) 4.6 mm, 3 \(\upmu\)m) was used for detection of trifurlain in the supernatant [37]. Trifluralin analysis was conducted using 70% acetonitrile and 30% water as mobile phase at a flow rate of 1.5 mL/min. The column was maintained at 30 \({}^{\circ}\)C and the injection volume was 10 \(\mu\)L. Trifluralin detection was programmed at 254 nm wavelength by the UV detector. Breeze(r) software was used to control the HPLC system and collect data. Diazinon and paraquat were analyzed using a Waters Acquity(r) ultra performance LC/MS/MS (Milford, MA, USA) equipped with triple quadrupole and methods previously described [38; 39]. For diazinon, an Acquity(r) BEH C18 column (\(2.1\times 50\) mm, \(1.7\) mm) was used and kept at \(35\)\({}^{\circ}\)C. A gradient elution using \(10\) mM ammonium acetate (eluent A) and \(10\) mM ammonium acetate in methanol (eluent B) was carried out (eluent B, \(10\)-\(90\%\) linear gradient for \(8\) min) at a flow rate of \(0.6\) mL/min. A sample volume of \(5\)\(\mu\)L was used for each analysis.