Influence of calcination atmosphere on adsorptive performance of composite minerals materials

• Three CMM were prepared under conditions of air, vacuum and nitrogen respectively.
• Three CMM had properties of porous, low density, and large specific surface area.
• The capacity of CMM to adsorb MG was more than 190 mg·g− 1, calcinated under vacuum.
• The probable pathway for the efficient and re-utilizing adsorbent has been proposed.

The three composite minerals materials, CMM-1, CMM-2 and CMM-3, which were prepared by four Chinese nonmetallic minerals (sodium bentonite, graphite, metakaolin and rectorite) and calcinated under the atmospheres of air, vacuum and nitrogen respectively, have been studied for the removal of malachite green (MG), a cationic dye, from aqueous solution. The influences of the three calcination atmospheres on the adsorbents' adsorptive performance were evaluated by a batch study in consideration of factors, such as the adsorbent dosage, initial dye concentration, adsorption duration, varied pH and static regeneration. Experimental results suggested that the maximum capacity of CMM to adsorb MG was more than 190 mg·g− 1, which was calcinated under the atmosphere of vacuum. Their adsorption equilibrium and kinetics confirmed the typical pseudo-first-order, pseudo-second-order, Freundlich and Langmuir adsorption models. The thermodynamic parameters of ΔGƟ, ΔHƟ and ΔSƟ showed that the adsorption was an exothermic and spontaneous process without remarkable change. The spent adsorbents were regenerated five times and probable pathway for the efficient and re-utilizing adsorbent has been proposed. The results indicate that CMM could be employed as porous, low density, and large specific surface area alternatives for the removal of cation dyes from industrial wastewater. The optimum adsorption capacity of the adsorbents was discovered under the calcination condition in vacuum.