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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.

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Effect of adsorbent dose on phosphate adsorption (pH:5, phosphate concentration: 50 mg/L, contact time: 60 min)
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Fig7: Effect of adsorbent dose on phosphate adsorption (pH:5, phosphate concentration: 50 mg/L, contact time: 60 min)

Mentions: The influence of dosage of algae–Mo and plain algae on phosphate removal is shown in Fig. 7. By increasing the dose of algae–Mo and plain algae from 2 to 10 g/L, the phosphate adsorption was increased from 39 to 98.7 and 24 to 63%, respectively. This finding may be due to increasing adsorbents’ surface area and thus the availability of more adsorption sites resulting from the increase in dosage (Asgari et al. 2014). It is noticeable from Fig. 7 that in the dosages higher than 10 g/L, no significant changes in the phosphate removal efficiency were observed. The increase of adsorbent dose (more than 10 g/L) would raise the collision probability between different adsorbent particles, which would lead to the overlapping and aggregating of the particles and would reduce the efficient utilization of functional groups on the adsorbent surface, and then influence the phosphate adsorption removal (Ye et al. 2015). Therefore, adsorbent dosage of 10 g/L was selected for the following tests. Generally, the result is supported by other studies (e.g., Liu et al. 2016; Ye et al. 2015), where an increase in phosphate adsorption was observed with an increase in the dose of adsorbent.Fig. 7


Modification of Sargassum angustifolium by molybdate during a facile cultivation for high-rate phosphate removal from wastewater: structural characterization and adsorptive behavior
Effect of adsorbent dose on phosphate adsorption (pH:5, phosphate concentration: 50 mg/L, contact time: 60 min)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig7: Effect of adsorbent dose on phosphate adsorption (pH:5, phosphate concentration: 50 mg/L, contact time: 60 min)
Mentions: The influence of dosage of algae–Mo and plain algae on phosphate removal is shown in Fig. 7. By increasing the dose of algae–Mo and plain algae from 2 to 10 g/L, the phosphate adsorption was increased from 39 to 98.7 and 24 to 63%, respectively. This finding may be due to increasing adsorbents’ surface area and thus the availability of more adsorption sites resulting from the increase in dosage (Asgari et al. 2014). It is noticeable from Fig. 7 that in the dosages higher than 10 g/L, no significant changes in the phosphate removal efficiency were observed. The increase of adsorbent dose (more than 10 g/L) would raise the collision probability between different adsorbent particles, which would lead to the overlapping and aggregating of the particles and would reduce the efficient utilization of functional groups on the adsorbent surface, and then influence the phosphate adsorption removal (Ye et al. 2015). Therefore, adsorbent dosage of 10 g/L was selected for the following tests. Generally, the result is supported by other studies (e.g., Liu et al. 2016; Ye et al. 2015), where an increase in phosphate adsorption was observed with an increase in the dose of adsorbent.Fig. 7

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.