Phosphate Removal by Anion Binding on Functionalized Nanoporous Sorbents

Abstract

Phosphate was captured from aqueous solutions by cationic metal-EDA complexes anchored inside mesoporous silica MCM-41 supports (Cu(II)-EDA-SAMMS and Fe(III)-EDA-SAMMS). Fe-EDA-SAMMS was more effective at capturing phosphate than the Cu-EDA-SAMMS and was further studied for matrix effects (e.g., pH, ionic strength, and competing anions) and sorption performance (e.g., capacity and rate). The adsorption of phosphate was highly pH dependent; it increased with increasing pH from 1.0 to 6.5, and decreased above pH 6.5. The adsorption was affected by high ionic strength (0.1 M of NaCl). In the presence of 1000-fold molar excess of chloride and nitrate anions, phosphate removal by Fe-EDA-SAMMS was not affected. Slight, moderate and large impacts were seen with bicarbonate, sulfate and citrate anions, respectively. The phosphate adsorption data on Fe-EDA-SAMMS agreed well with the Langmuir model with the estimated maximum capacity of 43.3 mg/g. The material displayed rapid sorption rate (99% of phosphate removal within 1 min) and lowering the phosphate content to ~ 10 µg/L of phosphorus, which is lower than the EPA's established freshwater contaminant level for phosphorous (20 µg/L).

Diversity of phytoplankton in some domestic wastewater-fed urban fish pond ecosystems of the Chota Nagpur Plateau in Bankura, India

“…Actually COND is a primary indicator of alteration in aquatic system and it depends on natural flooding, evaporation and pollution load. It is noted that an increase in water COND decreases the phosphorus availability to the phytoplankton that results in decline of phytoplankton populations (Chouyyok et al 2010;López-Flores et al 2014). The average COND in seven sites is 272-431 μS cm −1 which is lower than safe limits (2000 μS cm −1 ) of freshwater lakes criteria (Kemker 2015), and it indicates healthy pond ecosystem.…”

One-pot synthesis of Fe(III)-coordinated diamino-functionalized mesoporous silica: Effect of functionalization degrees on structures and phosphate adsorption

“…In the presence of AAPTS as organosilane in the synthesis gel, diamino-functionalized silica absorbents can be fabricated via a new F --assisted co-condensation method. After the removal of template (surfactant P123), the dimino-functional groups coordinate with Fe(Ш) to form Fe 3+ -en complexes as trapping centers, onto which phosphate anions can directly bound [28].…”

“…When the pH value is lower than 2.13, the predominant species of phosphate is the neutral H 3 PO 4 , which is weakly attached to the sites of S15-NN-Fe-0.5. However, Fe 3+ may leach out from S15-NN-Fe-0.5 at low pH [28], On the other hand, with the addition of weak base anions Cl − or NO 3 − , the degrees of removal for S15-NN-Fe-0.5 are slightly lower, which are 85.71% and 79.44%, respectively. In Figure 11, in addition to HCO 3 − , SO 4 2-exhibit a relatively strong effect on the phosphate removal, which may be not only related to its strong base strength, but also the geometry of tetrahedral anions which would well match the 3-fold symmetry structure of metalated en-functionalized mesoporous silica [64].…”

Fabrication of Fe-coordinated diamino-functionalized SBA-15 with hierarchical porosity for phosphate removal

“…Functionalization of mesoporous silicas and subsequent metal-impregnation can effectively generate specific binding sites for phosphate anions, thus forming phosphate adsorbents with a superior adsorption capacity and a fast adsorption rate [2,3]. For instance, the Fe(III)-coordinated diamino-functionalized SBA-15 exhibited the maximum phosphate capture capacity of 20.7 mg P/g and reached almost 90% of the final adsorption capacity in 10 min [4].…”