Abstract
Introduction: The growing textile industry has posed a prudent threat to already depleting freshwater resources. Therefore, it is essential to treat dyes from effluents prior to their discharge using some low-cost adsorbents in the scenario of developing countries like Pakistan.
Objectives: The current manuscript deals with the screening of agriculture and forest waste adsorbents for removal of hazardous malachite green (MG) dye. Further white cedar sawdust (WCS) is first ever explored for preferential MG dye adsorption potential and process optimization.
Methods: Process variables of MG dye adsorption onto WCS are optimized in batch reactors. Analytical techniques of FTIR, SEM and BET were used to identify various functional groups, surface morphology and surface area of WCS respectively. Different adsorption isotherm and kinetic models were applied to obtain theoretical data of MG adsorption onto WCS at variable initial dye concentrations of 30 - 100 mg L-1. Spontaneity and enthalpy of the system was investigated through thermodynamic studies. Moreover, WCS is also explored for preferential adsorption of MG dye in binary component system with orange II (OII) dye. After adsorption, the residual dye concentration was determined at 616 nm and 485 nm for MG and OII, respectively, using UV-Visible spectrophotometer.
Results: Increasing initial dye concentration, adsorbent dose and pH increased the adsorption of MG onto WCS. The primary and secondary macroporosity and functional groups (O-H, O-CH3, C-O, C-OH, C-H) were involved in the adsorption of MG dye. Adsorption data followed pseudo- second order kinetic and Langmuir (R2=0.999) models. MG biosorption process was spontaneous at higher temperatures. The adsorption of MG and OII dyes shrink by 21% and 60%, respectively, during the binary system as compared to single component system.
Conclusion: WCS can be successfully utilized as an alternative low-cost adsorbent for the treatment malachite green dye from aqueous solution. This adsorbent remain effective for MG dye adsorption by 80% if it is used for the treatment of binary component system.