Citric acid treatment of flax, cotton and blended nonwoven mats for copper ion absorption

The removal of metal ions from polluted water and wastewater with biodegradable, natural products is an area of current interest in the environmental arena. The objective of this study is to determine whether nonwoven mats made of biodegradable, natural fibers of flax and cotton can be used for remediation of a ubiquitous pollutant of water and wastewater, namely, copper ion. Nonwoven mats manufactured with flax or cotton fiber and flax/cotton fiber blends were treated with citric acid in order to enhance the amount of negative charge on the mats and improve their ability to sequester copper ion. The treated mats were monitored for changes in copper ion adsorption and fabric strength and compared to non-treated mats and process control mats. The results show that mats made from 100% flax and 75%/25% flax/cotton blends were similar to each other and significantly better at copper ion absorption than 100% cotton or 50%/50% flax/cotton blended nonwoven mats. Citric acid treatment, however, diminished mat strength compared to untreated mats for all samples; strength was similar for all treated nonwoven mats after correction for variable mat thickness. Treated flax fiber mats and flax/cotton fiber mats represent a potentially fast and convenient method for removal of metal ions from water and wastewater streams at an approximate cost of $1.40/m2 of mat.