Removal of Phosphorus from an Aqueous Solution by Nanocalcium Hydroxide Derived from Waste Bivalve Seashells: Mechanism and Kinetics

Abstract

Excessive supply of phosphorus, a vital macronutrient for all organisms, can cause unwanted environmental consequences such as eutrophication. An increase in agricultural and industrial activities has created a considerable imbalance in the phosphorus cycle with continuing adverse effects on sustainability and ecosystem health, thereby stipulating/postulating the significance of phosphorus removal. A unique and sustainable concept for the removal of phosphorus through the utilization of waste bivalve seashells was proposed in the present study. Flat-surfaced and hexagonally shaped nanocalcium hydroxide particles (∼96% purity) with size ranging from 100 to 400 nm have been synthesized, and phosphorus from its aqueous solution is treated via precipitation. An optimization study has been conducted using the Box−Behnken design of response surface methodology, which highlights that with a calcium/phosphorus mass ratio, pH, and temperature of 2.16, 10.20, and 25.48 °C, a phosphorus removal efficiency of 99.33% can be achieved in a residence time of 10 min. Also, under the same conditions, diluted human urine was analyzed and phosphorus removal efficiency of ∼95% was observed. Through experimental results, semiquantitative phase analysis, and transmission electron microscopy, it has been found that the reaction was diffusion-controlled, which was further confirmed through shrinking core diffusion modeling. The present study manifests the promising potential of waste seashell-derived nanocalcium hydroxide for phosphorus treatment and its precipitation in the form of value-added hydroxyapatite.

Adsorption kinetics and isotherms of binary metal ion aqueous solution using untreated venus shell

“…With decreasing C/C 0 , the metal ions were adsorbed onto the active adsorbent surface. The result showed the adsorption rate increased when more amounts of adsorbent were used, and consistent with the other studies [ 38 , 39 ]. At low dosages, the adsorption rate was relatively slow, and the process had not reached its equilibrium over the study period.…”

“…The –CO 3 groups were presented in both calcite and aragonite phases. Aragonite exhibited characteristic peak at 1081 cm −1 (symmetric stretching) and 856 cm −1 (out-of-plane bending) [ 39 ]. The combined spectra around 711 cm −1 could also consist of the peak corresponding to the CaO content presented on the shells [ 38 ].…”

Facile Fabrication of Calcium-Doped Carbon for Efficient Phosphorus Adsorption

“…Similar mechanisms were found in chemical reactions, and the slowest step was controlled by the internal diffusion process. 56 For CLDC800, physicochemical adsorption played a dominant role in the P removal process. The P adsorption capacities with CLDC800 were associated with the increase in its SSA and porosity.…”

New developments in biological phosphorus accessibility and recovery approaches from soil and waste streams

“…New approaches have been developed for foods that are not readily biodegradable, such as egg shells [67], sea shells, and fish scales [68] that are rich in biologically unavailable P. PSMs, such as the bacterial strain Acidovorax oryzae can be used to treat hydroxyapatite powder from tilapia fish scales ( Coptodon rendalli ) where 40% of initial 0.325 g P L –1 were recovered on lab‐scale [17]. Also, Bacillus megaterium was used on lab‐scale to recover P from poultry bones and ash after incineration [69].…”

“…The potential of biogenic materials that can be used for P precipitation is large and more promising than the use of, for example, magnesium, which is also on the EU list of critical raw materials. Bivalve seashells (mussels, scallops, oyster, Manila clam shell) can be used to obtain calcium hydroxide, which precipitates P as hydroxyapatite from diluted human urine with P recovery rate of 95% of initial 0.02 g P L –1 [68]. An extensive review on technologies used for wastewater treatment including biological P recovery is provided by Carrillo et al.…”