In a study, an adsorption process using hemp-based materials in felt form was applied to remove between 45 and 53 contaminants present in wastewater from the surface treatment industry. Several materials were compared using batch experiments, including a felt made of 100% hemp fiber (HEMP), the same felt cross-linked with 1,2,3,4-butanetetracarboxylic acid (HEMPBA), a felt coated with a maltodextrin-1,2,3,4-butanetetracarboxylic cross-linked polymer (HEMPM), and a felt coated with hydroxypropyl-a-cyclodextrin-1,2,3,4-butanetetra-carboxylic cross-linked polymer (HEMPCD). Chemical analysis showed that HEMPBA, HEMPM and HEMPCD materials had high adsorption capacities on metals in wastewater, confirming the role of carboxylic groups. Only HEMPCD was able to remove both metals and organics, resulting in the virtual elimination of organics such as chloroform, 1,2-dichlorobenzene, and nonylphenol. This result demonstrated the important role of cyclodextrin molecules in adsorption mechanism. HEMPCD also resulted in an important decrease in residual chemical oxygen demand and total organic carbon of more than 83% and 53%, respectively, while the treatment with HEMP lowered them by 12% and 12%, HEMPBA by 9% and 7%, and HEMPM by 45% and 26%. Chemical abatement and toxicity mitigation have demonstrated that adsorption onto a non-conventional material could be an interesting treatment step for the detoxification of wastewater .
Another study evaluated a model fungicide (difenoconazole) sorption capacity of two soils: soils alone, soils covered by hemp felt (raw or chemically modified by the grafting of cyclodextrin molecules) as an adsorbent material for limiting the dissipation of this molecule in the soil, and at the same time on felts alone. Adsorption in percolation and leaching experiments were also tested in the laboratory with a soil column. Soil alone adsorbed up to 99% of the percolating difenoconazole, whereas the use of modified hemp felt (HEMPCD) made it possible to limit soil storage to 26%, probably due to the formation of an inclusion complex with cyclodextrins. The trapping of difenoconazole molecules by the felt was not irreversible, as leaching with a CaCl2 solution resulted in the release of 60% of the amount initially fixed on raw hemp. However, only 22% of the amount fixed on HEMPCD was released, due to potentially stronger interactions with this material (host/guest type interactions between difenoconazole and cyclodextrin). 
1 Crini G, Bradu C, Cosentino C, Staelens J, Martel B, Fourmentin M, Loiacono S, Chanet G, Torri G, Morin-Crini N. Simultaneous Removal of Inorganic and Organic Pollutants from Polycontaminated Wastewaters on Modified Hemp-Based Felts. Rev. Chim.[internet]. 2021 Jan;72(1):25-43. Available from: https://doi.org/10.37358/RC.21.1.8401
2 Godeau, C., Morin-Crini, N., Staelens, J.N., Martel, B., Rocchi, S., Chanet, G., Fourmentin, M., Crini, G.
Adsorption of a triazole antifungal agent, difenoconazole, on soils from a cereal farm: Protective effect of hemp felt, Environmental Technology & Innovation, 22, 2021, 101394,