Abstract
The effect of heat treatment on the adsorptive capacity of a Brazilian palygorskite to remove the dyes crystal violet (CV) and congo red (CR) was investigated. The natural palygorskite was calcined at different temperatures (300, 500 and 700 °C) for 4 h. Changes in the palygorskite structure were evaluated using X-ray diffraction, X-ray fluorescence, thermogravimetric and differential thermal analysis, N2 adsorption/desorption and Fourier transform infrared spectroscopy. The adsorption efficiency of CV and CR was investigated through the effect of initial concentration, contact time, temperature, pH and dosage of adsorbent. The calcination increased the adsorption capacity of palygorskite, and the greatest adsorption capacity of CV and CR dyes occurred in the sample calcined at 700 °C (Pal-700T). The natural and calcined samples at 300 and 500 °C followed the Freundlich isothermal model, while the Pal-700T followed the Langmuir isothermal model. Adsorption kinetics results were well described by the Elovich model. Pal-700T showed better adsorption performance at basic pH, with removal greater than 98%, for both dyes. Pal-700T proved to be a great candidate for removing cationic and anionic dyes present in water.
Highlights
Water pollution due to the effluents discharged daily by various industries, such as textiles, pharmaceuticals, paper, plastics and cosmetics, is considered one of the biggest environmental problems in the world [1,2]
It is still possible to observe peaks characteristic of palygorskite in the Pal-500T sample; these reflections disappeared after heat-treatment at 700 ◦ C (Pal-700T)
These results show the adsorption of Palwas for both dyes was amplified after heat treatment
Summary
Water pollution due to the effluents discharged daily by various industries, such as textiles, pharmaceuticals, paper, plastics and cosmetics, is considered one of the biggest environmental problems in the world [1,2]. Effluents derived from these industries are often rich in dyes [3,4]. Dye pollution is a threat to human health and aquatic ecosystems since most of them are highly toxic, mutagenic, allergenic and carcinogenic, and can quickly accumulate in living cells, harming an entire food chain [5,6,7]. Human exposure to CV can cause eye irritation, increased heart rate, permanent blindness, respiratory disease, kidney failure, chemical cystitis and cancer [13,14,15,16,17]
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
