Simplifying Complex Contaminant Mixtures: Selective Ammonia Adsorption and Toxicity Reduction using 3D Printable Polymer–Zeolite

Evaluations of field sites containing multiple contaminants are commonly impacted by ammonia from anthropogenic and natural sources. Scientifically defensible lines of evidence regarding which contaminants cause toxicity inform management decisions. Methods are needed to isolate ammonia toxicity from other contaminant effects without the treatment confounding results. Treatment columns packed with zeolite remove ammonia, but loose powder cannot be recovered and can physically harm organisms. Solutions such as in situ bioassay cages containing resins or immobilizing zeolite in a non-toxic matrix are needed. This study employed 3D printable polylactic acid (PLA) to immobilize zeolite and enable on-demand customization of high surface area, deployable and retrievable structures. The impact of incorporating zeolite loadings (8–32% w/w) was investigated for relative efficacy. PLA–zeolite structures in ammonia-contaminated water indicated 24 h treatment reduced ammonia below toxic levels. To demonstrate efficacy for complex environmental samples, contaminated sediments were collected and used to prepare sediment–water slurries (elutriates) and analyzed for ammonia, metals and polyaromatic hydrocarbons (PAH) before and after treatment. The 32% zeolite composite reduced 44 mg/L ammonia-N by 74% (24 h) and 83% (48 h). Results indicated successful treatment of sediment elutriates by 3D printed PLA–zeolite in bioassay chambers, based on reduced toxicity to Ceriodaphnia dubia. The study provides evidence that in situ PLA–zeolite treatment did not alter metals or PAH concentrations, which is desirable for ammonia-specific toxicity reduction evaluations of complex samples. This technology is applicable to adsorption of other chemicals by integration of different adsorbent powders into printable polymer.