Cotton Filter Fabrics Functionalization by Chitosan UV-grafting for Removal of Dyes

Wastewater effluents from textile industry mainly contain dyes used in the dyeing or printing of textiles yarns or fabrics. A lot of technologies can be adopted for dye removal from wastewaters, including biological treatments based on activated sludge, adsorption on activated carbon, or membrane processes. Nevertheless, none of these methods is performing toward all classes of dyes; treatment plants of great dimensions and difficult handling can be required, while costs can be prohibitive. In a previous work we cationized cotton obtaining a strong improvement of dyes adsorption. In the present work, a cotton fabric was more eco-friendly functionalized by chitosan UV grafting and used as dyes adsorbent. The process parameters for the fabric treatment were optimized in terms of chitosan add-on, impregnation time, temperature, pH, radiation time and curing intensity. The cotton grafted by chitosan was characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared analysis in Attenuated Total Reflection (FTIR-ATR) and X-ray Photoelectron Spectroscopy (XPS). The material was then tested towards different dye classes: acid, reactive and direct dyes. Batch, kinetic as well as continuous flow assessment tests were carried out, evaluating the adsorption capacity by spectrophotometric measurements. Moreover the influence of pH as well as temperature on the adsorbent capacity of the functionalized cotton were investigated. The material showed good adsorption capacity and very high adsorption rate toward all the investigated dyes. Moreover, by assembling the functionalized cotton in a filter form, good adsorption capacity is ensured even at 25 degrees C, with good behaviour in terms of filter exhaustion and pressure drop while a positive influence on adsorption capacity was displayed in acid conditions. Finally, regeneration tests by NaOH solution were carried out, with a good release of the adsorbed dye. In conclusion, obtained results show good perspectives for chitosan treated cotton use in wastewater filtration.