A review of adsorbents engineered from biological materials developed to remediate estrogen pollution in the environment

Rising concerns over anthropogenic impacts on the environment have increased environmental pollution and water quality research which have demonstrated widespread pollutants characteristics in their low concentrations and few government regulations. Pharmaceuticals are an important subcategory of emerging contaminant pollution which consists of natural and synthetic compounds. Steroids are a notable class of pharmaceutical pollutants due to their high binding affinities and activation of signaling cascades at low concentrations. The impacts of hormonal pollutants necessitate remediation solutions. Adsorption technologies are a favorable method of pollutant removal in research due to the ease of implementation, cost-effectiveness, and potential for environmental friendliness. Biologically derived adsorbent materials offer additional potential benefits of employing properties of biological materials, improving biocompatibility, and valorizing biomass. Hydrogels, biomass, and biochar are some of the most environmentally friendly adsorbents in pollution remediation research and there is a sizable base of publications detailing promising results of these materials. Thus, a review of recent publications of hydrogels, biomass, and biochar applied to adsorb estrogens, the largest class of steroid hormones, will allow their findings to be compared. Estrone (E1), estradiol (E2), estriol (E3), and ethinylestradiol (EE2) were focused on in literature alongside other less-researched hormones including prednisolone, progesterone, hydrocortisone, and dexamethasone. Removal efficiencies of E1, E2, EE2, and E3 by hydrogels ranged from 10 % to 93 %, removal efficiencies of E2 and EE2 with biomasses reached up to 99 % with tree bark, and biochar adsorption peaked in capacity of 233 mg/g of EE2 when synthesized from spent mushroom substrate.