Abstract
In water and wastewater, phosphate anions are considered critical contaminants because they cause algae blooms and eutrophication. The present work aims at studying the removal of phosphate anions from aqueous solutions using silica particles functionalized with polyethylenimine. The parameters affecting the adsorption process such as pH, initial concentration, adsorbent dose, and the presence of competitive anions, such as carbonate, nitrate, sulfate and chromate ions, were studied. Equilibrium studies were carried out to determine their sorption capacity and the rate of phosphate ions uptake. The adsorption isotherm data fitted well with the Langmuir and Sips model. The maximum sorption capacity was 41.1 mg/g at pH 5, which decreased slightly at pH 7. The efficiency of phosphate removal adsorption increased at lower pH values and by increasing the adsorbent dose. The maximum phosphate removal was 80% for pH 5 and decreased to 75% for pH 6, to 73% for pH 7 and to 70% for pH 8, for initial phosphate concentration at about 1 mg/L and for a dose of adsorbent 100 mg/L. The removal rate was increased with the increase of the adsorbent dose. For example, for initial phosphate concentration of 4 mg/L the removal rate increased from 40% to 80% by increasing the dose from 0.1 to 2.0 g/L at pH 7. The competitive anions adversely affected phosphate removal. Though they were also found to be removed to a certain extent. Their co-removal provided an adsorbent which might be very useful for treating waters with low-level multiple contaminant occurrence in natural or engineered aquatic systems.
Highlights
Phosphorus, as a nutrient in water, enters the environment from municipal, industrial, human and natural sources
The purpose of this study was to investigate the use of amorphous silica materials functionalized with polyethyleneimine for the effective removal of phosphate anions from aqueous solutions, with prominence on treating water with phosphate concentrations less than 20 mg/L, and the study of the possible co-removal of other anionic pollutants that may be simultaneously present in the water
We studied the possible co-removal of other anionic pollutants that may be present in the water, such as chromates and nitrates
Summary
Phosphorus, as a nutrient in water, enters the environment from municipal, industrial, human and natural sources. Phosphorus enters water systems naturally by dissolving out of rock, but phosphates are mined and made into chemical fertilizers to grow crops. Human activities like improper disposal of municipal and industrial effluents and indiscriminate applications of agrochemicals in agriculture are the main factors contributing to the deterioration of water quality [1]. Elevated phosphate concentrations cause an adverse effect on the environment, favoring algae growth and subsequently eutrophication. Concentrations of phosphorus are currently unregulated in drinking water, phosphate concentrations ranging from 0.03 to 0.1 mg/L is associated with algae blooms [2]. Lack of phosphate in the environment can cause side effects. The natural resources of phosphate, which are phosphate ores, are rapidly being exhausted. Nowadays removal of phosphate as well as recovery of phosphate, are both of great significance [4]
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