Resource Recycling of Red Soil to Synthesize Fe2O3/FAU-type Zeolite Composite Material for Heavy Metal Removal

Summary

This article presents a novel and convenient route to synthesize Fe₂O₃/faujasite (FAU)-type zeolite composite material from red soil. The detailed synthesis parameters have been finely tuned. The obtained composite material can be used for efficient heavy metal-contaminated water remediation, indicating its potential applications in environmental engineering.

Abstract

Heavy metal-polluted water is of great concern to human health and the eco-environment. In situ water remediation techniques enabled by highly efficient adsorption materials are of great importance in these circumstances. Among all the materials used in water remediation, iron-based nanomaterials and porous materials are of great interest, benefiting from their rich redox reactivity and adsorption function. Here, we developed a facile protocol to directly convert the widely spread red soil in south China to fabricate the Fe₂O₃/faujasite (FAU)-type zeolite composite material.

The detailed synthesis procedure and synthesis parameters, such as reaction temperature, reaction time, and the Si/Al ratio in the raw materials, have been carefully tuned. The as-synthesized composite materials show good adsorption capacity for typical heavy metal(loid) ions. With 0.001 g/mL Fe₂O₃/FAU-type zeolite composite material added to different heavy metal(loid)-polluted aqueous solutions (single type of heavy metal(loid) concentration: 1,000 mg/L [ppm]), the adsorption capacity was shown to be 172, 45, 170, 40, 429, 693, 94, and 133 mg/g for Cu (II), Cr (III), Cr (VI), As (III), Cd (II), Pb (II), Zn (II), and Ni (II) removal, respectively, which can be further expanded for heavy metal-polluted water and soil remediation.

Introduction

Heavy metal(loid)s from anthropogenic and natural activities are ubiquitous in the air, water, and soil environment¹. They are of high mobility and toxicity, posing a potential health risk to human beings by direct contact or via food chain transportation². Water is vital for the life of human beings since it is the feedstock of every family. Restoring water health is crucial. Therefore, it is of great importance to decrease the mobility and bioavailability of toxic heavy metal(loid)s in water. To maintain good health in water, water remediation materials, such as biochar, iron-based materials, and zeolite, play an essen....

Protocol

1. Raw material collection and treatment

1. Red soil collection
   1. Collect the red soil. Remove the 30 cm top layer of the soil containing plants and residual organic matter.
      NOTE: In this experiment, the red soil was collected at the campus of Southern University of Science and Technology (SUSTech), Shenzhen, Guangdong, China (113°59' E, 22°36' N).
2. Red soil treatment
   1. Air-dry the collected red soil at room temperature and filter it through a 30-mesh sieve. Remove most of the large stones and leaves. Measure the heavy metal(loid) concentration (Table 1) in ....

Results

Figure 1 illustrates the overall synthesis route of zeolite based on the "soil for soil remediation" strategy⁶. With a simple organic-free route, red soil can be converted to Fe₂O₃/FAU-type zeolite composite material without adding any Fe or Al source. The as-synthesized zeolite composite material exhibits excellent removal capacity for heavy metal-polluted water remediation and can be used for soil remediation.

Discussion

Zeolite is typically an aluminosilicate material. In theory, materials that are rich in silicate and aluminate can be chosen as raw materials for zeolite synthesis. The Si/Al ratio of the raw material must be similar to that of the selected type of zeolite to minimize the usage of additional silicon/aluminum sources^6,8,16. The Si/Al ratio of FAU-type zeolite is 1.2, and the Si/Al ratio of red soil is 1.3. Therefore, red soil is .......

Materials

Name	Company	Catalog Number	Comments
Chemicals
Cadmium nitrate tetrahydrate	Shanghai Aladdin Bio-Chem Technology Co., LTD	C102676	AR, 99%. Make 1,000 ppm  stock solution for the test of adsorption performance of zeolite.
Chromium(III) nitrate nonahydrate	Shanghai Aladdin Bio-Chem Technology Co., LTD	C116446	AR, 99%. Make 1,000 ppm  stock solution for the test of adsorption performance of zeolite.
Copper sulfate pentahydrate	Shanghai Aladdin Bio-Chem Technology Co., LTD	C112396	AR, 99%. Make 1,000 ppm  stock solution for the test of adsorption performance of zeolite.
Lead nitrate	Shanghai Aladdin Bio-Chem Technology Co., LTD	L112118	AR, 99%. Make 1,000 ppm stock solution for the test of adsorption performance of zeolite.
Nickel nitrate hexahydrate	Shanghai Aladdin Bio-Chem Technology Co., LTD	N108891	AR, 98%. Make 1,000 ppm  stock solution for the test of adsorption performance of zeolite.
Nitric acid	Shanghai Aladdin Bio-Chem Technology Co., LTD	N116238	AR, 69.2%. Used as solvent in ICP-MS test.
Potassium dichromate	Shanghai Aladdin Bio-Chem Technology Co., LTD	P112163	AR, 99.8%. Make 1,000 ppm  stock solution for the test of adsorption performance of zeolite.
Silicon dioxide	Shanghai Aladdin Bio-Chem Technology Co., LTD	S116482	AR, 99%. For synthesis of zeolite.
Sodium (meta)arsenite	Sigma-aldrich	S7400-100G	AR, 90%. Make 1,000 ppm stock solution for the test of adsorption performance of zeolite.
Sodium hydroxide	Shanghai Aladdin Bio-Chem Technology Co., LTD	S111502	Pellets. For the synthesis of zeolite.
Zinc nitrate hexahydrate	Shanghai Aladdin Bio-Chem Technology Co., LTD	Z111703	AR, 99%. Make 1,000 ppm  stock solution for the test of adsorption performance of zeolite.
Equipment
Air-dry oven	Shanghai Yiheng Technology Instrument Co.,LTD.	DHG-9075A	Used for hydrothermal crystallization and drying of sample
Analytical balance	Sartorius Scientific Instruments Co.LTD	BSA224S-CW	Used for weighing samples
Centrifuge tubes	Nantong Supin Experimental Equipment Co., LTD
High speed centrifuge	Hunan Xiang Yi Laboratory Instrument Development Co.,LTD	H1850	Used for separation of solid and liquid samples
Multipoint magnetic stirrer	IKA Equipment Co.,LTD.	RT15	Used for stirring samples
Oscillator	Changzhou Guohua Electric Appliances Co.,LTD.	SHA-B	For uniform mixing of samples
Syringe-driven filter	Tianjin Jinteng Experimental Equipment Co.,LTD.		0.22 μm. For filtration.
Softwares
JADE 6.5	Materials Data& (MDI)
Mercury	Cambridge Crystallographic Data Centre (CCDC)
Materials Studio	Accelrys Software Inc.
Websites
Database of Zeolite Structures: http://www.iza-structure.org/databases/
ICSD: https://icsd.products.fiz-karlsruhe.de/en