Journal
JOURNAL OF ENVIRONMENTAL CHEMICAL ENGINEERING
Volume 5, Issue 3, Pages 2189-2199Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.jece.2017.04.021
Keywords
Natural phosphate; Adsorption; Desorption; Congo Red; Rhodamine 6G; Isotherm; Kinetics
Categories
Funding
- European Commission
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Moroccan natural phosphate was tested as an effective adsorbent for the removal of cationic dye rhodamine 6G (Rh6G) as well as anionic dye congo red (CR) from wastewater. The X-ray diffraction, FTIR and EDX characterizations reveal that the sample contains 98 wt% fluoroapatite (Ca-5(PO4)(3)F) with 1 wt% quartz (SiO2) and 1 wt% calcium carbonate (CaCO3). Nitrogen sorption analysis shows that the BET specific surface area (S-BET) and BJH pore volumes of the sample are 18.8 m(2)/g and 0.1 cm(3)/g, respectively. Batch adsorption experiments of the dyes from aqueous solution were conducted, taking into account the influence of initial dye concentration (100-400 mg/L), adsorbent dosage (1-20 g/L), contact time (5-300 min) and solution pH (3-12). The Langmuir isotherm model best represents the equilibrium adsorption process of the two dyes. The calculated maximum adsorbed quantity q(max) of CR and Rh6G at dosage 20 g/L and pH value of 5.2 were found 19.81 and 6.84 mg/g, respectively. The adsorption of Rh6G and CR on natural phosphate was found to follow the pseudo-second-order model. Natural phosphate was also tested as an effective adsorbent for a simulated dye effluent under industrial conditions of temperature and pH. Desorption studies were conducted using HCl as an eluent and the highest elution efficiency for both dyes was obtained with a 0.1 M solution. Accordingly, it is demonstrated in this work that natural phosphate is a very efficient adsorbent for both cationic and anionic dyes from contaminated water, and represents a great low-cost alternative to commercial adsorbents due to its abundance as a natural resource in Morocco.
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