Orange-derived and lemon-derived adsorbents with controlled grain for an efficient elimination of some cationic and anionic dyes

Abstract

This study aims to demonstrate that orange-derived and lemon-derived systems can be used in continuous processes as efficient adsorbents to the entrapment of some anionic and cationic dyes in the textile dyeing wastewater effluents. Physically and chemically modified orange and lemon mesocarps are used as natural adsorbents for the cationic dyes Basic Blue 3, Basic Yellow 21, Basic Red 18 and Basic Green 4 and the anionic dyes Acid Blue 264, Acid Yellow 49 and Acid Red 337, all commonly used in the textile dyeing industry. Adsorption capacities of the orange-derived and lemon-derived adsorbents on the dyes are studied simulating a batch and continuous industrial processes. Results demonstrate that treated orange mesocarp (orange-derived adsorbent) can adsorb up to 97% of cationic Basic Green 4 in 30 min, whereas the lemon mesocarp (lemon-derived adsorbent) can retain up to 88% within the same time. In the case of anionic, 91% Acid Blue 264 is adsorbed by the orange mesocarp in 15 min, whereas 92% is adsorbed by the lemon homologue within the same time. As far as the authors know, physically and chemically modified orange and lemon mesocarps have not been used on the removal of cationic (Basic Blue 3, Basic Yellow 21, Basic Red 18 and Basic Green 4) and anioinic (Acid Blue 264, Acid Yellow 49 and Acid Red 337) dyes of textile dyeing wastewater industry. It is a costless and efficient treatment that supposes, on the one hand, an eco-friendly and feasible process for discolouration of wastewater and, on the other, a valorisation (upcycling) of orange and lemon peels, which are not currently used.