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Modification of Sargassum angustifolium by molybdate during a facile cultivation for high-rate phosphate removal from wastewater: structural characterization and adsorptive behavior

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ABSTRACT

In this paper, a new and facile approach for molybdate loading in the brown algae of Sargassum angustifolium is introduced. The molybdate ions were entered into the algae body during a short cultivation to produce algae–Mo as a novel adsorbent for eliminating phosphate ions from synthetic and real wastewaters. Results of the surface analysis showed that molybdate loading onto the algae was successfully performed. Herein, basic variables, such as initial solution pH, adsorbent dosage, contact time, phosphate concentration, and temperature, were investigated in detail to assess the phosphate adsorption performance of algae–Mo. The pseudo-second-order kinetic model fitted our acquired experimental kinetic data most appropriately, in comparison to the use of a pseudo-first-order model. The Langmuir model appeared to fit the adsorption data more desirably than that of Freundlich and Dubnin–Radushkevich models, with a maximum phosphate adsorption capacity of 149.25 mg/g at 25 °C. The finding of the thermodynamic study revealed that the phosphate adsorption onto algae–Mo was spontaneous, feasible, and endothermic in nature. The study on Mo2+ ions leaching strongly suggested that the risk of Mo2+ leakage during phosphate adsorption was negligible at a wide pH range of 3–9. The adsorption efficiency attained was 53.4% at the sixth cycle of reusability. Two real wastewaters with different qualities were successfully treated by the algae–Mo, suggesting that the algae–Mo could be ordered for practical wastewater treatment.

No MeSH data available.


Kinetic models of a pseudo-first-order model, b pseudo-second-order model (adsorbent dose 10 g/L, pH 5)
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Fig9: Kinetic models of a pseudo-first-order model, b pseudo-second-order model (adsorbent dose 10 g/L, pH 5)

Mentions: Phosphate adsorption experimental data were fitted to the most well known of kinetic models, namely the pseudo-first-order and the pseudo-second-order model. The correlation coefficient (R2) and kinetic information obtained from the aforementioned models (displayed in Fig. 9) for the different initial concentrations of phosphate have been presented in Table 4. The fitted linear regression plots (Fig. 9) and the results of fitting models (Table 4) showed that the experimental data obtained from the phosphate adsorption by algae–Mo had the best fit with the pseudo-second-order model for the investigated concentration (30, 50, and 70 mg/L) with the higher coefficients of determination (R2 > 0.999) than those of the pseudo-first-order model. Therefore, the rate of phosphate adsorption onto the algae–Mo is of pseudo-second order, suggesting that the adsorption of phosphate onto the adsorbent is influenced by both the adsorbate and the adsorbent concentrations under the investigated conditions (Asgari et al. 2013b). In addition, as can be seen from Table 4, the difference between the experimental qe values and the model-calculated qe is very small (less than 2%), reaffirming the high correlation of adsorption to the pseudo-second-order model. The decrease of k2 values with increase in the initial phosphate concentration showed a good concordance between the experimental data and the pseudo-second-order kinetic model. A review of the recently published literature (Hamoudi and Belkacemi 2013; Li et al. 2014; Riahi et al. 2013) on the phosphate adsorption showed that most researchers reported that the pseudo-second-order model satisfactory fits the experimental data.Fig. 9


Modification of Sargassum angustifolium by molybdate during a facile cultivation for high-rate phosphate removal from wastewater: structural characterization and adsorptive behavior
Kinetic models of a pseudo-first-order model, b pseudo-second-order model (adsorbent dose 10 g/L, pH 5)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120031&req=5

Fig9: Kinetic models of a pseudo-first-order model, b pseudo-second-order model (adsorbent dose 10 g/L, pH 5)
Mentions: Phosphate adsorption experimental data were fitted to the most well known of kinetic models, namely the pseudo-first-order and the pseudo-second-order model. The correlation coefficient (R2) and kinetic information obtained from the aforementioned models (displayed in Fig. 9) for the different initial concentrations of phosphate have been presented in Table 4. The fitted linear regression plots (Fig. 9) and the results of fitting models (Table 4) showed that the experimental data obtained from the phosphate adsorption by algae–Mo had the best fit with the pseudo-second-order model for the investigated concentration (30, 50, and 70 mg/L) with the higher coefficients of determination (R2 > 0.999) than those of the pseudo-first-order model. Therefore, the rate of phosphate adsorption onto the algae–Mo is of pseudo-second order, suggesting that the adsorption of phosphate onto the adsorbent is influenced by both the adsorbate and the adsorbent concentrations under the investigated conditions (Asgari et al. 2013b). In addition, as can be seen from Table 4, the difference between the experimental qe values and the model-calculated qe is very small (less than 2%), reaffirming the high correlation of adsorption to the pseudo-second-order model. The decrease of k2 values with increase in the initial phosphate concentration showed a good concordance between the experimental data and the pseudo-second-order kinetic model. A review of the recently published literature (Hamoudi and Belkacemi 2013; Li et al. 2014; Riahi et al. 2013) on the phosphate adsorption showed that most researchers reported that the pseudo-second-order model satisfactory fits the experimental data.Fig. 9

View Article: PubMed Central - PubMed

ABSTRACT

In this paper, a new and facile approach for molybdate loading in the brown algae of Sargassum angustifolium is introduced. The molybdate ions were entered into the algae body during a short cultivation to produce algae–Mo as a novel adsorbent for eliminating phosphate ions from synthetic and real wastewaters. Results of the surface analysis showed that molybdate loading onto the algae was successfully performed. Herein, basic variables, such as initial solution pH, adsorbent dosage, contact time, phosphate concentration, and temperature, were investigated in detail to assess the phosphate adsorption performance of algae–Mo. The pseudo-second-order kinetic model fitted our acquired experimental kinetic data most appropriately, in comparison to the use of a pseudo-first-order model. The Langmuir model appeared to fit the adsorption data more desirably than that of Freundlich and Dubnin–Radushkevich models, with a maximum phosphate adsorption capacity of 149.25 mg/g at 25 °C. The finding of the thermodynamic study revealed that the phosphate adsorption onto algae–Mo was spontaneous, feasible, and endothermic in nature. The study on Mo2+ ions leaching strongly suggested that the risk of Mo2+ leakage during phosphate adsorption was negligible at a wide pH range of 3–9. The adsorption efficiency attained was 53.4% at the sixth cycle of reusability. Two real wastewaters with different qualities were successfully treated by the algae–Mo, suggesting that the algae–Mo could be ordered for practical wastewater treatment.

No MeSH data available.