Abstract
In this 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.
Highlights
The European policy on water pollution results from the Water Framework Directive (WFD, Directive 2000/60/EC) of 2000, which established guidelines for the protection of surface water, underground water and coastal water in Europe
Four hemp-based materials were compared using batch experiments, a felt made of 100% hemp fiber, the same felt cross-linked with 1,2,3,4-butanetetracarboxylic acid, a felt coated with a maltodextrin-1,2,3,4-butanetetracarboxylic cross-linked polymer, and a felt coated with hydroxypropylβ-cyclodextrin-1,2,3,4-butanetetracarboxylic cross-linked polymer [26,27,28,29,31]
The process and associated chemical pathway to produce a 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-β-cyclodextrin-1,2,3,4-butanetetracarboxylic cross-linked polymer (HEMPCD) have been detailed elsewhere [26,27,30,31,32,33,34]
Summary
The European policy on water pollution results from the Water Framework Directive (WFD, Directive 2000/60/EC) of 2000, which established guidelines for the protection of surface water, underground water and coastal water in Europe. The WFD classified chemicals into two main lists of priority substances (Directive 2006/11/EC). The second includes priority substances such as trichlorobenzene, octylphenols, dichloromethane, lead and nickel, which are considered less toxic than those of the first list, but present a significant risk to the environment. The surface treatment industry is affected by many of these substances [13]. Since the 2000s, Europe is asking industry to innovate to reduce and/or to eliminate chemicals present in their waters, i.e. wastewaters and discharge waters. Considerable efforts have been made by the industry in general, and surface treatment industry in particular, over the last 20 years, the problem of water pollution remains a significant concern. The industrial sector continues to look into new treatment methods to decrease the levels of pollution present in their wastewaters [1,4,5]
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