Abstract
Contamination of water with Malachite green (MG) may threaten aquatic and human life. Nitrogen-fixing Azotobacter sp. is an efficient adsorbent for the removal of MG from dye solutions. The optimum pH for the biosorption process was determined. The maximum adsorption capacity and the effect of different adsorbate concentrations were detected. The kinetics and isotherm models for biosorption were constructed. Optimum adsorption of MG by Azotobacter sp. was obtained at pH 6.0, biomass concentration was 0.05%, initial dye concentration was 50 mg.L-1, and contact time was 600 mins. Dye adsorption exhibited an increase with contact time and initial malachite green concentration. The kinetics of the adsorption process was best followed by the pseudo-second-order kinetic model which confirms the chemisorption process. The adsorption equilibrium data fit well to the Langmuir model indicating a monolayer adsorption behavior onto a surface of Azotobacter sp. with a finite number of active sites. Maximum biosorption capacity was found to be 142.8 mg.g-1 of bacterial biomass. The dry biomass of Azotobacter sp. has proved to be an efficient biosorbent for the removal of synthetic dyes from actual industrial effluent that is contaminated with up to 400 mg.L-1 dye concentration.
Highlights
Malachite green (MG) is a cationic triphenylmethane dye that is extensively used in many industries such as textile, pharmaceutical, and the aquaculture industry (Nath & Ray 2015; Wu et al 2020)
Functional groups that are found in the cell wall of Azotobacter sp. are carboxyl, sulfate, and amine
At low pH solutions, the protonation of functional groups enhances a net positive charge on Azotobacter sp. This allows the electrostatic repulsion of malachite green dye molecules that are positively charged which led to a decrease in the malachite green removal (Sekhar et al 2009; Nath & Ray 2015)
Summary
Malachite green (MG) is a cationic triphenylmethane dye that is extensively used in many industries such as textile, pharmaceutical, and the aquaculture industry (Nath & Ray 2015; Wu et al 2020). The major sector of the economy worldwide mainly depends upon the textile industry; this has led to an increase in the release of large amounts of organic chemicals including dyes and many inorganic chemicals in industrial effluents and wastewater (Kumar et al 2006). The discharge of these pollutants in the aquatic environment may alter the chemical, physical and biological characteristics of the aquatic system (Erdem et al 2005; Dos Santos et al 2007). The US Food and Drug Administration (FAD) has nominated MG as a priority chemical for carcinogenicity investigations
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
