Volume Change Behavior of Phosphogypsum Treated Clayey Soils Contaminated With Inorganic Acids – A Micro Level Study

Abstract

Soils exhibit undesirable volume changes when exposed to high concentrations of acids, which is manifested most frequently in the beds of foundations of industrial establishments associated with their production or use. However, control of this phenomenon has received less attention than it deserves. This paper aims to investigate the mineralogical and micro-structural changes occurred during the volume change behavior of phosphogypsum treated clayey soils contaminated with sulfuric acid and phosphoric acid solutions. Oedometer test results showed high swelling and low compressibility for acid contaminated soils than that of water. The change in microstructure towards flocculated fabric along with mineralogical transformations are responsible for the volume changes in soils. The mineralogical changes that affected the volume change behavior are discussed with FT-IR, XRD and SEM analysis. Phosphogypsum treatment was found to be effective in controlling volume changes in soils with phosphoric acid, whereas in the case of sulfuric acid found to be futile.

A Review of Solidification/Stabilization of Heavy Metal Contaminated Soil

“…There are vast stockpiles of the fertilizer industry by-product, phosphogypsum, that pose environmental and human health problems since they are not used as quickly as they are created. Chavali [70] investigate phosphogypsum as a soil stabilizer, agricultural fertilizer, and controller in cement manufacturing, road construction, and building materials [71,72]. Phosphogypsum is a stabilizer that may be applied alone or in combination with other compounds to enhance the design behavior of soils [71,[73][74][75].…”

“…Excessive use of phosphogypsum may lead to heaving, and structural disturbance, weakening cement stabilized dredged soil, according to Zang et al [81]. It has also been used to counteract the effects of phosphoric acid on soil volume [70].…”

Selective Leaching and Recovery of Er, Gd, Sn, and In from Liquid Crystal Display Screen Waste by Sono-Leaching Assisted by Magnetic Separation

“… 9 − 11 Despite being efficient and fast, these media are detrimental to the environment and to human health because they generate effluents with a high level of contamination. 12 , 13 Furthermore, these techniques are not selective, requiring complicated subsequent separation processes.…”

“…Currently, REE recycling is mainly focused on permanent magnets, fluorescent lamps, and Ni–MH (nickel–metal hydride) batteries using pyrometallurgical methods for REE alloys, gas phase extraction methods (where REEs are transferred to a volatile chloride phase), and hydrometallurgical methods. These last mainly employ inorganic acid leaching with nitric, sulfuric, and hydrochloric acids. − Despite being efficient and fast, these media are detrimental to the environment and to human health because they generate effluents with a high level of contamination. , Furthermore, these techniques are not selective, requiring complicated subsequent separation processes.…”

Experimental Study of the Usage of Combined Biopolymer and Plants in Reinforcing the Clayey Soil Exposed to Acidic and Alkaline Contaminations

“…When the soil is eroded by acidic or alkaline pollutants (e.g., acid rain, industrial wastewaters, etc. ), its physicochemical and mechanical properties change accordingly, in terms of Atterberg limits [26][27][28], compressibility [29,30], and mechanical strength [26,27,[31][32][33][34][35].…”