Removal of Phosphate by Ivory Coast Shale in a Homogeneous Reactor and Under Hydrodynamic Conditions: Influence of Soluble Species

Abstract

Developing low cost and effective phosphate adsorbents is crucial to prevent eutrophication of natural waters. Here, phosphate removal by a natural and abundant shale from the Ivory Coast was investigated in both batch and column experiments with special attention devoted to understand the adsorption process. Batch experiments were carried out to assess the influence of initial phosphate concentration, sorbent dosage, contact time, and pH on phosphate removal. The phosphate removal efficiency increased with increased shale dosage while phosphate uptake decreased. Aqueous Ca, Mg, Al, and Fe species concentrations decreased in the presence of phosphate. Additionally, phosphate uptake strongly decreased with pH increases in the range 2–11, but then increased at pH 12. The kinetics were well described using a pseudo-second order model, and Langmuir adsorption isotherms were used for the equilibrium surface reactions. Adsorption to nanoparticles of goethite was hypothesized to be the major phosphate removal mechanism in the pH range 4–10. Column experiments with a flow rate of 1 mL min−1 and an initial phosphate concentration of 25 mg L−1 showed a breakthrough point at a V/Vp value of ~17, where Vis the volume of phosphate solution added to the column and Vp is the pore volume. A V/Vp value of ~17 corresponded to a phosphate uptake of 0.17 mg/g, which was in agreement with the batch experiments. Column experiments revealed a strong correlation between the aqueous concentrations of Ca, Mg, Al, and Fe species and phosphate removal and, thus, suggest that phosphate removal by the shale occurred by aqueous dissolution/precipitation.

Reactive Materials in the Removal of Phosphorus Compounds from Wastewater—A Review

“…Shales of a larger fraction size also offer poorer efficiency in removing phosphorus due to their lower surface area and higher hydraulic conductivity than smaller material particles [23,24]. Likewise, recent column studies confirmed the maximum sorption capacities for material of 0.06 and 0.23 g P/kg, where the initial mg P/L concentrations were 5 and 25, respectively [25]. Further, the amount of porosity (the ratio of the volume of voids inside the material to the volume of the whole body) did not affect the sorption capacity of shale.…”

Triazolone/alginate-zinc (II)-montmorillonite sustained release system with improved adsorption capacity and pH-sensitivity

“…For example, Jain et al [5] adopted montmorillonite (Mt) to prepare Mt-based alginate beads as a delivery vehicle for oral administration of drugs which can effectively reduce the multiple dosing frequency. Besides, the prepared sustained release system usually showed pH-sensitivity as the universal characteristic of clay minerals [19] which was beneficial to the pest control in agriculture [20][21][22]. And the addition of montmorillonite to formulation was found to have a profound inhibitory effect on the release of pesticide reported by previous research [23].…”

Phosphorus and Nitrogen Removal by Saturated Vertical-Flow Constructed Wetlands (SVCWs) Type Micro-Pilot Using Shale from Ivory Coast as a Substrate

“…aluminum oxide (17.5%) and iron oxide (10.2%). There is also a minority presence of magnesium oxide (2.1%) manganese oxide (0.6%) and calcium oxide (0.4%) as shown Table 1 (Kpannieu et al, 2018).…”

“…The uniformity of the particle-size distribution (the uniformity coefficient) was calculated as the ratio between d 60 and d 10 ; according to the literature, materials of 0.2 -1 mm effective size and uniformity coefficient less than 3 are appropriate for substrates of constructed wetlands (Knowles et al, 2011;Mallet et al, 2013). The corresponding values of shale presented in Table 1 satisfy the above-mentioned requirements (Kpannieu et al, 2018). Porosities were determined from the amount of water needed to saturate a known volume of shale and the bulk density of the shale (g•cm −3 ) were based on the ratio between the dry weight and the bulk volume of the sands.…”