Fixed-Bed Column Technique for the Removal of Phosphate from Water Using Leftover Coal.

Dereje Tadesse Mekonnen,Bernd Lennartz,Esayas Alemayehu

doi:10.3390/ma14195466

Dereje Tadesse Mekonnen, Bernd Lennartz + Show 1 more

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https://doi.org/10.3390/ma14195466

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Abstract

The excessive discharge of phosphate from anthropogenic activities is a primary cause for the eutrophication of aquatic habitats. Several methodologies have been tested for the removal of phosphate from aqueous solutions, and adsorption in a flow-through reactor is an effective mechanism to reduce the nutrient loading of water. This research aimed to investigate the adsorption potential of leftover coal material to remove phosphate from a solution by using continuous flow fixed-bed column, and analyzes the obtained breakthrough curves. A series of column tests were performed to determine the phosphorus breakthrough characteristics by varying operational design parameters such as adsorbent bed height (5 to 8 cm), influent phosphate concentration (10–25 mg/L), and influent flow rate (1–2 mL/min). The amorphous and crystalline property of leftover coal material was studied using XRD technology. The FT-IR spectrum confirmed the interaction of adsorption sites with phosphate ions. Breakthrough time decreased with increasing flow rate and influent phosphate concentration, but increased with increasing adsorbent bed height. Breakthrough-curve analysis showed that phosphate adsorption onto the leftover coal material was most effective at a flow rate of 1 mL/min, influent phosphate concentration of 25 mg/L, and at a bed height of 8 cm. The maximal total phosphate adsorbed onto the coal material’s surface was 243 mg/kg adsorbent. The Adams–Bohart model depicted the experimental breakthrough curve well, and overall performed better than the Thomas and Yoon–Nelson models did, with correlation values (R2) ranging from 0.92 to 0.98. Lastly, leftover coal could be used in the purification of phosphorus-laden water, and the Adams–Bohart model can be employed to design filter units at a technical scale.

Highlights

Increasing concern about the effect of phosphate released from different natural and human activities has resulted in more stringent environmental policies in recent years
The small peaks shown at the bands of 537.92 and 471.98 cm−1 in the Fourier transform infrared (FT-IR) spectrum of the leftover coal material belong to the bending vibration of Si–O–Si bonds [43,58]
The adsorption performance and the breakthrough-curve characteristics of the column were influenced by influent phosphate concentration, adsorbent bed height, and the influent flow rate of the solution

Summary

Introduction

Increasing concern about the effect of phosphate released from different natural and human activities has resulted in more stringent environmental policies in recent years. Phosphate is one of the main nutrients for plants and aquatic lives, and is, in turn, primarily responsible for the eutrophication of water [1,2,3,4,5,6]. The eutrophication of water bodies due to phosphate discharges is a challenging issue for industrialized regions [7,8]. Detergent-making industries, and mining companies are the primary sources for phosphate discharged to water bodies. The uncontrolled use of fertilizers releases phosphate and affects nearby water streams due to the runoff from agricultural activities [9,10]. Water pollution by phosphate is tremendously increasing, and demand for the removal of excess phosphate from water bodies is thereby increasing [11]

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