Effects of pH on leaching behavior of compacted cement solidified/stabilized lead contaminated soil

Abstract

The compacted cement stabilized/solidified (S/S) metal contaminated soil could be used for “controlled utilization,” such as road base, quarry rehabilitation, and lagoon closure. However, the complexity and variability of environment, especially the acid rain and alkaline leachate, greatly influence the leaching behaviors of S/S heavy metal contaminated soil and threaten the environment. The leaching characteristics of the compacted S/S samples were investigated over a wide range of pH (2.65, 3.65, 5.00, 7.00, and 10.00). Semidynamic leaching tests were conducted to evaluate the effects of pH on effectiveness and controlling leaching mechanism of compacted cement S/S treated lead (Pb) contaminated soil. Results showed that there was no obviously change of the cumulative fraction of Pb leached (CFL) in weak acid or weak alkaline conditions (pH ranging from 5.00 to 10.00), and the strong acid significantly altered the leaching behaviors of Pb. The calculated values of effective diffusion coefficient (De) and leachability index (LX) indicated that the mobility of Pb2+ was weak and the compacted S/S treatment could be used for “controlled utilization” with environment pH value ranging from 3.65 to 10.00. Especially, the LX value was 8.49 when the compacted S/S sample was immersed in the leachant with pH 2.65, indicated that the S/S sample was not considered appropriate for disposal. The mechanism controlling Pb2+ leaching from S/S samples at all the pH range (2.65–10.00) appeared to be diffusion, and with pH decreasing in acid conditions, the controlling leaching mechanism somehow was changing from diffusion to surface wash‐off. © 2015 American Institute of Chemical Engineers Environ Prog, 35: 149–155, 2016

Mechanical Properties and Leaching Characteristics of Geopolymer‐Solidified/Stabilized Lead‐Contaminated Soil

“…Artificially contaminated soil was used in this test due to its high repeatability and homogeneity. Pb-contaminated soils were obtained by mixing a Pb(NO 3 ) 2 solution with air-dried clean soil until the Pb(NO 3 ) 2 concentration in the soil reached 10000 mg/kg, which represents a universal concentration for Pbcontaminated soil in China [11][12][13]. Deionized water was then added to the contaminated soil until the water content reached 23.5% (optimum moisture content).…”

Leachability and Stability of Hexavalent-Chromium-Contaminated Soil Stabilized by Ferrous Sulfate and Calcium Polysulfide

“…The detailed description of the physical characterization of the raw soil and Cr(VI)-contaminated soil are presented in Table 1, which was obtained according to the "Standard for soil test method" of China. The Light Proctor compaction method was used for the compaction test [16,17]. Cr(VI)-contaminated soils were obtained by adding K 2 Cr 2 O 7 solution until the Cr(VI) content in the soil reached 1000 mg/kg, which represents a universal content for Cr(VI)-contaminated soil in China [18][19][20][21][22].…”

A Study on influence of organic ligands on migration of heavy metals through compacted clayey soil

“…This is due to increase of negative charge in the soil solid phase (Sherene 2010) with increase in pH which leads to higher mobility of (VI) and also the mobility was expected to be increased by probable decrease in the plastic limit of the soil after interaction of Cr (VI) with the soil. Hence, it increases the hydraulic conductivity of the tested soils due to decrease in the thickness of diffused double layer (Wang P. et al, 2015).  Composite heavy metal system…”