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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.


EDS spectrum of algae–Mo a before and b after phosphate adsorption
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Fig3: EDS spectrum of algae–Mo a before and b after phosphate adsorption

Mentions: Surface analysis showed that algae–Mo particles had a BET multipoint surface area of 1.44 m2/g and a total pore volume of 0.0497 cm3/g. Because the BET surface area of the adsorbent is relatively low, the functional groups may have a more important role than particle surface area (Ramavandi et al. 2016). The pHzpc of algae–Mo was obtained to be 5.4, signifying a negative surface charge for a working solution pH greater than 5.4 and a positive surface charge for a solution pH below 5.4. According to Fig. 1, the pore sizes of the modified algae before and after phosphate removal falls within the range of 2–50 nm, indicating that the algae–Mo adsorbent was a mesoporous type. The surface structures of the fresh and phosphate-loaded algae–Mo particles imaged at the same magnification are displayed in Fig. 2. As shown in Fig. 2a, the fresh adsorbent was a porous and smooth surface material. Figure 2b depicts algae–Mo after adsorption, indicating that phosphate ions were adsorbed evenly on the surface of algae–Mo. EDS spectra of adsorbent before and after phosphate adsorption (Fig. 3a, b) confirmed this observation. The results of elemental analysis of the algae–Mo for phosphate adsorption are presented in Table 1. As seen from Table 1, it is obvious that the algae were successfully modified by the molybdate element and the phosphate ion adsorbed by algae–Mo. The presence of phosphate on the adsorbent (~13.5 wt%) proved that the phosphate removed from the wastewater had been adsorbed onto the algae–Mo. On a closer look at Table 1, it is clear that only 0.04% of Mo was lost during the adsorption, indicating the good stability of the algae–Mo adsorbent.Fig. 1


Modification of Sargassum angustifolium by molybdate during a facile cultivation for high-rate phosphate removal from wastewater: structural characterization and adsorptive behavior
EDS spectrum of algae–Mo a before and b after phosphate adsorption
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig3: EDS spectrum of algae–Mo a before and b after phosphate adsorption
Mentions: Surface analysis showed that algae–Mo particles had a BET multipoint surface area of 1.44 m2/g and a total pore volume of 0.0497 cm3/g. Because the BET surface area of the adsorbent is relatively low, the functional groups may have a more important role than particle surface area (Ramavandi et al. 2016). The pHzpc of algae–Mo was obtained to be 5.4, signifying a negative surface charge for a working solution pH greater than 5.4 and a positive surface charge for a solution pH below 5.4. According to Fig. 1, the pore sizes of the modified algae before and after phosphate removal falls within the range of 2–50 nm, indicating that the algae–Mo adsorbent was a mesoporous type. The surface structures of the fresh and phosphate-loaded algae–Mo particles imaged at the same magnification are displayed in Fig. 2. As shown in Fig. 2a, the fresh adsorbent was a porous and smooth surface material. Figure 2b depicts algae–Mo after adsorption, indicating that phosphate ions were adsorbed evenly on the surface of algae–Mo. EDS spectra of adsorbent before and after phosphate adsorption (Fig. 3a, b) confirmed this observation. The results of elemental analysis of the algae–Mo for phosphate adsorption are presented in Table 1. As seen from Table 1, it is obvious that the algae were successfully modified by the molybdate element and the phosphate ion adsorbed by algae–Mo. The presence of phosphate on the adsorbent (~13.5 wt%) proved that the phosphate removed from the wastewater had been adsorbed onto the algae–Mo. On a closer look at Table 1, it is clear that only 0.04% of Mo was lost during the adsorption, indicating the good stability of the algae–Mo adsorbent.Fig. 1

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.