Contaminated soil amendment by diatomite: chemical fractions of zinc, lead, copper and cadmium

Abstract

High concentration of labile metals in soil directly affects soil quality, water health and human safety. Decreasing mobility of metals, especially in contaminated soils, by cost-effective amendments may alleviate environmental problems. Natural diatomite was investigated to immobilize toxic elements of zinc, lead, copper and cadmium in a contaminated calcareous soil. The diatomite was characterized using X-ray fluorescence spectrometry and scanning electron microscopy. Contaminated soil was incubated with 0, 2 and 5 weight-% of diatomite at 25 °C for 8 weeks. Tessier sequential extraction method was also used as a suitable method for identification of chemical forms of heavy metals; metal stability index and mobility factor were calculated. Results showed that application of diatomite in soil significantly decreased the metals in the exchangeable fraction and increased them in the residual fraction. The exchangeable metal fractions decreased by 66-88%, and residual fractions increased by 18-94% in the 5 weight-% of diatomite treatment after 8-week incubation. With an increase in the amount of diatomite applied and the incubation time, metal mobility factor values significantly decreased and soil pH values increased. Application of diatomite caused the heavy metals redistribution toward more stable forms and leads to an increase in stability index values. In conclusion, in situ immobilization of heavy metals by application of diatomite, as a low-cost amendment, had a significant potential to stabilize metals in the contaminated calcareous soil.

Study on Properties of Copper-Contaminated Soil Solidified by Solid Waste System Combined with Cement

“…As a result, soil particles flocculate and coagulate [44] to increase the structure density and the strength. Meanwhile, Cu 2+ is also preserved on the soil surface; 3 Some cementitious substances hardened to form the skeleton, enhance strength and can wrap and bond heavy metal ions to form pellets so that the heavy metals are sealed and form a relatively stable spatial structure; 4 A large number of Ca(OH) 2 generated in pore solutions react with active substances such as SiO 2 and Al 2 O 3 dissolved in soil and red mud to produce secondary gel products, such as C-S-H, C-A-H, and C-A-S-H. As a result, a space network structure forms, the adhesion and stability between particles improve, and the volcano ash reaction occurs, which are the main factors promoting the strength of the solidified body in the later stage; 5 CaSO 4 dissolved in phosphogypsum can combine with Al 2 O 3 in an alkaline environment to form ettringite. This expansive acicular crystal cannot only fill the pores but can also increase the intercalation capacity of the hydration products and make the spatial structure of soil more compact [58], and heavy metal ions enter C-S-H or C-A-S-H and AFt crystals through replacement, which is the main mechanism of solidification; 6 In a strong alkaline pore solution saturated with Ca(OH) 2 , Cu 2+ is easily precipitated due to its low solubility and may form insoluble salts such as silicate, carbonate, and sulfate, which will reduce the migration ability of Cu 2+ and fix heavy metals.…”

“…Waste gas, water, and residue discharged from copper-zinc-ore-smelting areas and wastewater discharged from electroplating and metal processing inevitably cause serious copper pollution to the original site of the factory [2]. Soil polluted with heavy metals does not only seriously deteriorate its engineering properties [3] but the heavy metals in soil will also cause contamination to surrounding soil with rainwater scouring and groundwater circulation and may affect food safety and human health [4]. Therefore, there is an urgent need to develop effective technologies for the remediation of soil polluted with heavy metal ions to reduce environmental pollution.…”

Mobility of Zn and Cu in Bentonites: Implications for Environmental Remediation

“…Zinc (Zn) is an essential trace element supporting the immune system, but its excess can lead to immune system disorders and copper (Cu) deficiency; Cu aids enzymatic functions, but in excess, it causes liver and kidney damage [ 6 , 9 ]. The use of fertilizers containing high concentrations of Cu and Zn, industrial activities, and flotation tailings storage are the most common sources of these metals [ 10 , 11 , 12 ]. Both Cu and Zn are trace elements that play vital roles as essential nutrients for plants.…”

Single and Binary Adsorption Systems of Rhodamine B and Methylene Blue onto Alkali-Activated Vietnamese Diatomite

“…Besides, diatomite is abundant in nature, cheap, and environmentally friendly [11]. Several studies have dealt with the applicability of natural diatomite in the adsorption field [6,10,11,[21][22][23]. Other studies have focused on diatomite surface modification with metals or organic functional groups to improve adsorption efficiency or expand its applications [1,[7][8][9][24][25][26][27][28][29][30][31][32].…”