A Suppression Method for Elution of F−, [B(OH)4]−, AsO43−, and CrO42− from Industrial Wastes Using Some Inhibitors and Crushed Stone Powder

Masatoshi Endo,Xiaoxu Kuang,Atsushi Sasaki,Atsuki Sentoku

doi:10.3390/technologies6030079

Abstract

The disposal and the reuse of industrial wastes have become increasingly difficult due to the elution of hazardous anions, such as F−, [B(OH)4]−, AsO43−, and CrO42−. Effective methods for removing hazardous ions and reusing solid wastes are urgently required. In this study, Ca(OH)2, MgCl2, and BaCl2 were added to reduce the elution concentrations of F, B, As, and Cr by coprecipitating insoluble inorganic salts. After this, ordinary Portland cement (OPC) was added to the ion exchange and solidified with these hazardous ion-containing substances. The addition of crushed stone powder (CSP), which was a by-product of the process of crushing aggregates or sawing stone, inhibited the elution of hazardous ions and improved the inhibition effect of OPC. The elution concentrations of F, B, As, and Cr were successfully reduced from their maximum elution concentration of 10 mg/L to below the environmental standards values of Japan. A simultaneous inhibition method for the elution of F, B, As, and Cr from industrial wastes has been developed successfully and would be able to promote the reuse and recycling of CSP and other industrial wastes.

Highlights

Fluoride (F, F− ), boron (B, [B(OH)4 ]− ), arsenate (As(V), AsO4 3− ), and chromium (Cr(VI), CrO4 2− ), which are eluted from industrial wastes, such as slag, incineration ash, and so on, are usually present as anions and oxyanions
The aim of this study is to develop an effective method to suppress the elution of F−, [B(OH)4 ]−, AsO4 3 −, and CrO4 2 − from industrial wastes and to improve the reuse and recycling of crushed stone powder (CSP) and other industrial wastes
A decrease in the elution concentrations of F, B, As, and Cr was observed with an addition of CSP (Table 1)

Summary

Introduction

Fluoride (F, F− ), boron (B, [B(OH)4 ]− ), arsenate (As(V), AsO4 3− ), and chromium (Cr(VI), CrO4 2− ), which are eluted from industrial wastes, such as slag, incineration ash, and so on, are usually present as anions and oxyanions. Law of Japan [1] stipulate that the maximum concentration values of F, B, As(V), and Cr(VI) are 0.8, 1.0, 0.01, and 0.05 mg/L, respectively. It is difficult to remove these harmful ions due to their high solubility. The disposal and the reuse of hazardous ion-containing industrial wastes have become increasingly important. In Japan, intermediate waste treatment, such as burning, crushing, and so on, has been carried out to reduce the quantity of the industrial wastes. There are still about 17.2 million cubic meters of wastes in 2014, which are left in landfills due to the presence of hazardous materials [2]

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Conclusion