Study of phosphate removal from aqueous solution by zinc oxide

Abstract

Zinc oxide (ZnO) was synthesized and used to investigate the mechanism of phosphate removal from aqueous solution. ZnO particles were characterized by X-ray diffraction, scanning electron microscope and Fourier transform infrared spectroscopy before and after adsorption. Batch experiments were carried out to investigate the kinetics, isotherms, effects of initial pH and co-existing anions. The adsorption process was rapid and equilibrium was almost reached within 150 min. The adsorption kinetics were described well by a pseudo-second-order equation, and the maximum phosphate adsorption capacity was 163.4 mg/g at 298 K and pH ∼6.2 ± 0.1. Thermodynamic analysis indicated the phosphate adsorption onto ZnO was endothermic and spontaneous. The point of zero charge of ZnO was around 8.4 according to the pH-drift method.Phosphate adsorption capacity reduced with the increasing initial solution pH values. The ligand exchange and Lewis acid-base interaction dominated the adsorption process in the lower and the higher pH range, respectively. Nitrate, sulfate and chloride ions had a negligible effect on phosphate removal, while carbonate displayed significant inhibition behavior.

Assessment of the Different Type of Materials Used for Removing Phosphorus from Wastewater

“…Phosphorus adsorption capacities and phosphorus removal efficiency, R, (%) were determined from the Equations (3) and (4) respectively: where V (mL) represents the working solution volume, C 0 and C e (mg/L) are the concentrations in the working solution (initial phosphorus concentration) and filtrate (equiibrum phosphorus solution), respectively, and m (g) is the adsorbent amount [ 89 ].…”

“…The specific procedure was as follows: 0.1 g of each adsorbent material was weighed into a 50 mL Erlenmeyer flask, 15 mL of a set concentration of phosphorus solution was added, and the pH of the solution was adjusted to 7.5 with 0.1 mol/L hydrochloric acid or 0.1 mol/L sodium hydroxide solution. The solution was shaken in a constant temperature shaker at 180 r/min and 25 °C for 24 h. A syringe was used to take out 10 mL of the supernatant from the Erlenmeyer flask and filter it with a 0.45 µm filter membrane; the phosphorus concentration in the filtrate was determined by ammonium molybdate spectrophotometry (950 Lambda UV-Vis-NIR Perkin Elmer, Waltham, MA, USA), and the removal capacity of phosphorus and phosphorus removal efficiency of each adsorbent was calculated according to Equations (3) and (4) [ 83 , 89 ]. A single-factor analysis method was used and blank and two parallel experiments were carried out.…”

“…For each adsorbent material the following procedure was used: 150 mL of a 400 mg/L phosphate solution was mixed with 0.1 g of adsorbent (adsorbent to solution ratio = 1:25) size in a series of 200 Erlenmeyer flasks. The pH of solution was 7.5 (adjusted with 0.1 mol/L hydrochloric acid or 0.1 mol/L sodium hydroxide solution) [ 83 , 89 ]. The flasks were kept at room temperature (25 °C) and 180 rpm, and samples were collected at different time intervals; phosphorus concentration was determined by ammonium molybdate spectrophotometry, and the corresponding removal capacity was calculated [ 83 ].…”

Synthesis and Characterization of 2D Magnesium Oxide Nanoflakes: A Potential Nanomaterial for Effective Phosphate Removal from Wastewater

“…A similar study conducted by ma et al has shown that the morphology of MgO could be varied with the time at which the reaction is taken place at a particular temperature. [97] The product yield was increased up to 62 %, followed by repetitive autoclavation of the supernatant. The SEM images showed a phase change from MgO nanowires to nanoflakes.…”

Biosynthesis approach of zinc oxide nanoparticles for aqueous phosphorous removal: physicochemical properties and antibacterial activities

“…For various contact times, the P ion residual concentration was calculated (from 0 min to 24 h). The following equations (11)(12)(13)(14) were used to assess the adsorption data toward phosphorous following the kinetic models:…”