Removal of Phosphate from Eutrophic Lakes through Adsorption by in Situ Formation of Magnesium Hydroxide from Diatomite

Abstract

Since in situ formation of Mg(OH)2 can efficiently sorb phosphate (PO4) from low concentrations in the environment, a novel dispersed magnesium oxide nanoflake-modified diatomite adsorbent (MOD) was developed for use in restoration of eutrophic lakes by removal of excess PO4. Various adsorption conditions, such as pH, temperature and contact time were investigated. Overall, sorption capacities increased with increasing temperature and contact time, and decreased with increasing pH. Adsorption of PO4 was well described by both the Langmuir isotherm and pseudo second-order models. Theoretical maximum sorption capacity of MOD for PO4 was 44.44-52.08 mg/g at experimental conditions. Characterization of PO4 adsorbed to MOD by use of X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and solid state (31)P nuclear magnetic resonance revealed that electrostatic attraction, surface complexation and chemical conversion in situ were the major forces in adsorption of PO4. Mg(OH)2 formed in situ had a net positive charge on the surface of the MOD that could adsorb PO4(3-) and HPO4(2-) anion to form surface complex and gradually convert to Mg3(PO4)2 and MgHPO4. Efficiency of removal of PO4 was 90% when 300 mg MOD/L was added to eutrophic lake water. Results presented here demonstrated the potential use of the MOD for restoration of eutrophic lakes by removal of excess PO4.

Struvite crystallization combined adsorption of phosphate and ammonium from aqueous solutions by mesoporous MgO⿿loaded diatomite

“…The BET surface area and total pore volume of MgO-D were 34.780 m 2 g -1 and 0.195 cm 3 g -1 which were far more than raw diatomite. Similar results were reported in previous work [20]. The pHzpc of MgO-D (11.07) was quite different to raw diatomite (5.59) according to …”

“…V (L) is the volume of adsorption solution and m is the adsorbent weight (g). interconnected into a lattice-like network leading to significant improvement of surface area and total pore volume of diatomite [20].…”

“…Diatomite is abundant in China with low cost, small particle size, high thermal stability, and high porosity [20], and has been considered as potentially efficient adsorbents in water treatment [21]. However, raw diatomite exhibits a relatively low adsorption capacity due to poor specific surface area.…”

Distribution patterns and dynamics of phosphorus forms in the overlying water and sediment of Dongting Lake

“…(Table 1) (Fig. 5) (Crossman et al, 2013;Xie et al, 2013). The maximum adsorption of P in sediment (Qm) can be obtained using the Langmuir equation to evaluate the enrichment degree and release risk of P in the sediment (Huang et al, 2013).…”

A New Method for Phosphorus Recovery Using Magnesium Alloy Electrode under Tensile Stress

“…The point at which the current was 0 mA was shifted toward the anodic direction upon the addition of potassium hydrogen phosphate under a tensile stress of 10 MPa, attributable to the formation of basic phosphate compounds, such as magnesium phosphate tribasic salts. Magnesium hydroxides, hypothesized to be formed on the alloy surface in this study, have been able to adsorb phosphates effectively for the improvement of the water quality of entropic lakes [13]. After deposition of phosphorous under 10 MPa, 90 mg/L of phosphorous concentration was determined in the slurry.…”