Microfibers release during washing and, removal by tamarind fruit shell carbon filters: Subsequent utilization in crystal violet dye removal from water

Abstract

The release of synthetic microfibers (MFs) into the environment has been correlated to the laundering of clothes due to mechanical and chemical stresses preferably during hand washing based on conventional brushing practices. At this juncture, the present research explores the possible release of MFs in water by brush washing experiments on nylon and polyester clothes using four different quality brushes. The ejection of MFs from fabric as a function of brushing time (1 – 4 h), brushing area, quality of brushes and cloth type was investigated. The lengths of MFs were dominated mostly in the range of 100 – 200 μm and 200 – 400 μm along with the presence of microplastics (MPs) as threads, tubules and granules. The fabric materials were characterized using Fourier – Transform Infrared (FTIR) and Scanning Electron Microscope (SEM) with Elemental Dispersive Spectroscopy (EDS) techniques before and after the brush washing experiments. The pyrolysis Gas Chromatography – Time of Flight – Mass Spectroscopic (Py – GC-ToF-MS) study was performed to analyse the pyrolyzate products from the extracted MFs and MPs. Furthermore, the study was further extended into the abatement of MFs/MPs in wastewater samples discharged from the brush washing studies using acid washed tamarind fruit carbon (ATFSC) by columnar technique. The total time of 186 h at a flow rate of 1.7 mL per minute was spent for treating 19 L of wastewater samples with 3480 MFs (WW – 1) and 2858 MFs (WW – 2) as a consequence of brush washing experiments. It was apparent from the microscopic examination that the MFs remain undetectable till 12.24 litres of wastewater (1 & 2) samples which passed through the column for 120 h. The ATFSC (AT) resulting after the filtration followed by thermal treatment was converted as barium alginate/carbon composites. These composites were found efficient in removing 83 % of crystal violet from aqueous solution at pH 7.97 for an equilibrium time of 90 min. The corresponding adsorption kinetics revealed the compliance of pseudo – second – order model with respect to domination of chemical forces during sorption. The present research not only explores the elimination of MFs/MPs from wastewater but also the possible conversion in the form of carbon composites followed by application in the removal of crystal violet from water.