Green-Engineered Barrier Creams with Montmorillonite-Chlorophyll Clays as Adsorbents for Benzene, Toluene, and Xylene

Abstract

Dermal exposures to hazardous environmental chemicals in water can significantly affect the morphology and integrity of skin structure, leading to enhanced and deeper penetration. Organic solvents, such as benzene, toluene, and xylene (BTX), have been detected in humans following skin exposure. In this study, novel barrier cream formulations (EVB^™) engineered with either montmorillonite (CM and SM) or chlorophyll-amended montmorillonite (CMCH and SMCH) clays were tested for their binding efficacy for BTX mixtures in water. The physicochemical properties of all sorbents and barrier creams were characterized and were shown to be suitable for topical application. In vitro adsorption results indicated that EVB-SMCH was the most effective and favorable barrier for BTX, as supported by the high binding percentage (29-59% at 0.05 g and 0.1 g), stable binding at equilibrium, low desorption rates, and high binding affinity. Pseudo-second-order and the Freundlich models best fit the adsorption kinetics and isotherms, and the adsorption was an exothermic reaction. Ecotoxicological models using L. minor and H. vulgaris that were submersed in aqueous culture media showed that the inclusion of 0.05% and 0.2% EVB-SMCH reduced BTX concentration. This result was further supported by the significant and dose-dependent increase in multiple growth endpoints, including plant frond number, surface area, chlorophyll content, growth rate, inhibition rate, and hydra morphology. The in vitro adsorption results and in vivo plant and animal models indicated that green-engineered EVB-SMCH can be used as an effective barrier to bind BTX mixtures and interrupt their diffusion and dermal contact.

Keywords: BTX; adsorption isotherm; barrier emulsion cream; bentonite clay; chlorophyll; dermal contact; ecotoxicological model; generally recognized as safe; kinetics; topical application.

Figure 1.

SEM images of CMCH (A–C) and SMCH (D–F).

Figure 2.

XRD patterns of CM (A), SM (B), CMCH (C), and SMCH (D).

Figure 3.

FT-IR spectra of parent CM and SM (A) and CMCH and SMCH (B).

Figure 4.

The percent reduction in the adsorption of (A) benzene, (B) toluene, and (C) xylene by various EVB formulations for 2 h (* p ≤ 0.05; ** p ≤ 0.01 compared to base EVB).

Figure 5.

Effect of initial chemical concentrations and contact time (for up to 4 h) on the adsorption of (A) benzene, (B) toluene, and (C) xylene in 0.05 g EVB and EVB-SMCH at 37 °C and pH 7.

Figure 6.

Effect of contact temperature on the adsorption of (A) benzene, (B) toluene, and (C) xylene on 0.05 g EVB and EVB-SM in pH 7 water for 2 h.

Figure 7.

Adsorption isotherms of (A) benzene, (B) toluene, and (C) xylene on surfaces of 25 mg EVB and EVB-SMCH at 37 °C in pH 7 water for 2 h, plotted by the Freundlich model. Data represent the mean adsorption (mg/kg) at each concentration, run in triplicate. Bands indicate 95% confidence intervals on the mean response.

Figure 8.

Dose-dependent toxicity of BTX on L. minor (A) frond number, (B) surface area of surviving plants, (C) chlorophyll content on Day 7, and (D) growth rate (bar graph) and inhibition percentage (line) (* p ≤ 0.05, ** p ≤ 0.01 compared to media control).

Figure 9.

Protection against BTX by EVBs at 0.2% in the L. minor medium on (A) frond number, (B) surface area of surviving plants, (C) chlorophyll content on Day 7, and (D) growth rate (bar graph) and inhibition percentage (line) (* p ≤ 0.05, ** p ≤ 0.01 compared to media control).

Figure 10.

Hydra toxicity from BTX (A) and protection by EVBs at 0.05% (B) and 0.2% (C). The hydra media control showed consistent scores of 10. Data represent the mean morphological score at each time point, run in triplicate (** p ≤ 0.01 compared to media control; ^## p ≤ 0.01 compared to BTX).