Synthesis of zeolite from fly ash and its adsorption of phosphorus in wastewater

Kecheng Zhang,Lizelle Van Dyk,Hengqin Zhao,Dongsheng He,Jie Deng,Shuang Liu

doi:10.1515/gps-2021-0032

Abstract

Abstract Using synthetic zeolite from fly ash to treat high concentration phosphorus wastewater does not only improve the utilization of fly ash as solid waste but also reduce the environmental pressure caused by eutrophication. A synthetic zeolite was prepared from coal fly ash by one-step hydrothermal synthesis and applied for phosphorus adsorption from industrial wastewater (∼8,000 mg-P/L), and its adsorption characteristics and performance were studied. The results indicated that the product was a well-crystallized Na-P1 zeolite with typical morphology of plate- and rod-shaped crystals. Compared with the original fly ash, the specific surface area and average pore volume of the synthetic zeolite were nine and six times larger than the fly ash, reaching 43.817 m2/g and 0.122 cm3/g. The results from phosphorus adsorption onto the synthetic zeolite showed that the synthetic zeolite had good phosphorus adsorption properties. The adsorption process highly conformed to the pseudo-second-order kinetic model with the regression coefficient R 2 of 0.998. Phosphorus adsorption on the synthetic zeolite was fitted to the Langmuir monolayer adsorption model, and the regression coefficient R 2 was 0.989. The maximum phosphorus adsorption capacity was 84.4 mg-P/g-zeolite.

Highlights

Phosphorus is an essential nutrient element in all organisms and plays an important role in the development of industry and agriculture, such as the production of chemical fertilizers, pesticides, detergents, and so on [1]
The US Environmental Protection Agency (EPA) recommends that if wastewater is discharged into lakes or reservoirs, the level of PO43− should not be higher than 0.05 mg/L [7]
The results showed that the adsorption of phosphorus by the synthetic zeolite was more in line with the pseudo-second-order kinetics with the regression coefficient of 0.998, and the fitted equilibrium adsorption capacity Qe value was close to the actual adsorption value, which indicated that the adsorption process of phosphorus was controlled by chemical adsorption [58]

Summary

Introduction

Phosphorus is an essential nutrient element in all organisms and plays an important role in the development of industry and agriculture, such as the production of chemical fertilizers, pesticides, detergents, and so on [1]. Large quantities of phosphorus wastewater is produced by industries, agricultural production, and daily life of humans. When a large amount of phosphorus wastewater is discharged into natural water, which increases the phosphorus content in water to above 0.02 mg/L, eutrophication will occur [2,3]. Algae and other aquatic plant life will flourish, resulting in a significant decrease in the dissolved oxygen content and the deterioration of water quality [4]. The growth of rooted aquatic macrophytes will interfere with navigation, aeration, and channel capacity, and the dead macrophytes and phytoplankton will cause microbial breakdown processes [4,6]. The US Environmental Protection Agency (EPA) recommends that if wastewater is discharged into lakes or reservoirs, the level of PO43− should not be higher than 0.05 mg/L [7]. It is necessary to remove phosphorus from water and wastewater to meet more stringent environmental regulations [8]

Objectives

Methods

Results