Adsorption of Pb2+ by ameliorated alum plasma in water and soil.

Ningyu Li,Qinglin Fu,Bin Guo,Chen Liu,Hua Li,Yongzhen Ding,Amit Bhatnagar

doi:10.1371/journal.pone.0210614

Ningyu Li, Qinglin Fu + Show 5 more

Open Access

https://doi.org/10.1371/journal.pone.0210614

Copy DOI

Abstract

Four methods, including hot acid treatment, hot alkali treatment, calcination treatment and sulfhydrylation treatment, were applied to activate alum plasma in order to obtain new Pb2+ adsorbents. The corresponding adsorption isotherm satisfies the Langmuir equation, and the maximum adsorption of the alum plasma after hot acid treatment, hot alkali treatment and high-temperature calcination were 18.9, 57.3 and 10.9 mg·g−1, respectively, and in the range of 1.23–6.57 times greater than the adsorption capacity of the original alum plasma. The soil culture experiments indicated that the effective Pb content in the soils treated with hot alkali ameliorated alum plasma was significantly lower (p < 0.05) than those treated with the other three types of alum plasma. For example, if the additive content is 5.0%, after a storage period of 16 weeks, the effective Pb content becomes 19.87 mg·kg−1, which corresponds to a reduction of 60.9% in comparison with the control sample. In addition, Specific surface area (BET), Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FIR) were used to characterize the microstructure of alum plasma before and after amelioration. It was evident that hot alkali treatment of alum plasma resulted in smaller particles, a significantly higher specific area and lower mineral crystallinity, which improved the adsorption performance of Pb2+. In conclusion, hot alkali treatment of alum plasma indicates relatively good Pb2+ adsorption ability, and is a promising novel adsorbents that could ameliorate soils that have been polluted by heavy metal Pb.

Highlights

Lead (Pb) is one hazardous pollutant that displays strong toxicity in soils, and is an important restricted element according to the safety standards of agricultural products
We have found that the basic structural unit of alum plasma is a silicon-oxygen tetrahedron and an aluminum-oxygen octahedron, which possess relatively stable chemical properties
The original alum plasma was treated using the following four treatment methods: Hot acidic ameliorated alum plasma (T1): the sieved alum plasma was mixed into a l mol L−1 HCl solution in order to prepare an alum pulp solution using a l:10 solid-liquid ratio (g mL−1)

Summary

Introduction

Lead (Pb) is one hazardous pollutant that displays strong toxicity in soils, and is an important restricted element according to the safety standards of agricultural products. It exists in soil in various forms, including a water-soluble state, ion-exchangeable state, organically bound state, carbonate bounded state and a residue state. The adsorption of Pb by plants in the soil primarily depends on the concentrations of water-soluble Pb and ion-exchangeable Pb [1]. The addition of a passivant could absorb/immobilize water-soluble Pb in the soil, lowering its accumulation in plants and animals, for example, in phosphate materials, alkaline matters, biochar and red mud, amongst other [2,3,4,5,6]. Following the introduction of adsorbents, the exchangeable, high-activity Pb in the soil transforms into a residual state that is low in activity.

Methods

Results

Conclusion