Removal of metal ions Cd (II), Pb (II), and Cr (III) from water by the cashew nut shell Anacardium occidentale L

• Published in: Ecological engineering 2014-12, Vol.73, p.514-525
• Main Authors: Coelho, Gustavo Ferreira, Gonçalves Jr, Affonso Celso, Tarley, César Ricardo Teixeira, Casarin, Juliana, Nacke, Herbert, Francziskowski, Marcio André
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Anacardium; Anacardium occidentale; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; Biosorption; Conservation, protection and management of environment and wildlife; Desorption; Economics; Environment and sustainable development; Environmental degradation: ecosystems survey and restoration; Fundamental and applied biological sciences. Psychology; Mathematical models; Metal ions; Removal; Scanning electron microscopy; Sustainability; Water contamination
• ISSN: 0925-8574; 1872-6992
• DOI: 10.1016/j.ecoleng.2014.09.103

•The cashew nut shell has the potential for removal of Cd, Pb and Cr of water.•The IR and SEM were favorable to adsorption characteristics.•Predominantly by chemisorption models pseudossegunda order and DR.•Occurrence of adsorption in both mono and multilayer for metals.•The cashew nut shell had a high desorption rate of Cd2+, Pb2+. Current paper analyzes the cashew nut shell (Anarcadium occidentale L.) (CNS11CNS: chasew nut shell.) as a natural adsorbent in the removal of the metal ions Cd2+, Pb2+, and Cr3+ from contaminated water. Adsorbent was characterized as to its chemical and structural composition by infra-red spectroscopy (IR22IR: infra-red spectroscopy.); as to its morphology by scanning electron microscopy (SEM33SEM: scanning electron microscopy.); and point of zero charge (pHPCZ44pHPCZ: point of zero charge.). Best adsorption conditions (pH, adsorbent mass, contact time) were determined. Adsorption kinetics was evaluated by pseudo-first order, pseudo-second order, Elovich and intra-particle diffusion mathematic models, whereas adsorption isotherms were linearized according to mathematical models by Langmuir, Freundlich and Dubinin–Radushkevich (D–R55D–R: Dubinin–Radushkevich.). The effects of initial concentration, temperature in the process, de-sorption and the comparison with activated coal were also performed. SEM and IR showed positive characteristics to adsorption. Further, pHPCZ of CNS lay between 3.69 and 4.01. Best adsorption conditions of the ions Cd2+, Pb2+, and Cr3+ were pH 5.0; adsorbent mass: 12gL−1; equilibrium time 60min. Pseudo-second order and D–R models suggested the predominance of chemo-sorption process. Adjustment of Langmuir and Freundlich models suggested adsorption in mono- and multi-layers. Thermodynamic study showed that the process was spontaneous for Cd2+ at 15 and 25°C. CNS had high desorption rates for Cd2+ and Pb2+, but low desorption with Cr3+. CNS has a potential to aggregate economical rate and increase the crop’s productive chain when the residue is used for the removal of Cd2+, Pb2+, and Cr3+ from water.