Removal of phenolphthalein and methyl orange from laboratory wastewater using tetraethylammonium modified kaolinite clay

Abstract

Developing an efficient technique for the treatment of laboratory wastewater is a challenge. In response, kaolinite clay (CLY) was functionalized with tetraethylammonium bromide to produce tetraethylammonium modified kaolinite clay (CLY@AM). Both CLY and CLY@AM were characterized with X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). CLY and CLY@AM were evaluated for their ability to remove phenolphthalein (PH) and methyl orange (MO) from laboratory wastewater. Peaks from FTIR and XRD suggests the formation of CLY@AM, while SEM micrograph revealed the surfaces of CLY and CLY@AM to be irregularly shaped while CLY@AM has some patches. The adsorption capacities exhibited by CLY@AM towards PH (43.00 ​mg ​g⁻¹) and MO (40.00 ​mg ​g⁻¹) were found more promising compared to CLY, which showed 20.00 and 22.00 ​mg ​g⁻¹ towards MO and PH, respectively. The ΔH^o value for the sorption of PH was found to be −71.7523 ​kJ ​mol⁻¹, while the value was −46.1826 ​kJ ​mol⁻¹ for MO. The ΔH^o values are negative in nature which suggests the process to be exothermic. The removal of MO and PH from the solution may be described by Langmuir isotherm with a regeneration capacity above 80% even at the 14th regeneration cycle. Applying CLY@AM towards the purification of raw laboratory wastewater contaminated with PH and MO further proves the effectiveness of CLAY@AM as a potentially efficient material for the purification of laboratory wastewater systems contaminated with PH and MO.