Chemical and environmental compatibility of red mud liners for hazardous waste containment

Abstract

Red mud residue from alumina production has been proposed as an alternative liner material. The chemical and environmental compatibility of red mud upon exposure to representative organic (methanol, heptane, TCE, and acetic acid) and inorganic liquids (CaCl 2 and seawater) was studied. Chemical compatibility assays comprised Atterberg limits and sedimentation and hydraulic conductivity tests for red mud interacted with the chemical liquids, whereas the environmental compatibility was assessed through the leaching of metals from red mud as permeated with the liquids. Methanol greatly reduced the plasticity at concentrations C80 % by volume, but it did not increase the hydraulic conductivity of compacted red mud. High concentrations (C60 % v/v) of acetic acid reduced the plasticity and enhanced the sedimentation of red mud. Conversely, acetic acid concentrations B40 % caused dispersion, but damaged the hydraulic properties and structure of red mud. The percolation of a pH 2 acetic acid solution did not adversely affect the hydraulic performance of the red mud liner. Neither diluted heptane nor TCE affected the red mud. However, pure organics suppressed the plasticity and induced aggregation of red mud, suggesting a great detrimental effect on red mud liners. The red mud exhibited great resistance to attack by inorganic salt solutions. Some concerning leaching of metals (primarily Al and Cr) occurred as water, acetic acid, and CaCl 2 solutions percolated through red mud, but effluent metals concentration quickly dropped to permissible levels. In general, red mud exhibited a high resistance against chemical attack; nevertheless, exposure to low-dielectric-constant organic chemicals should be avoided.

pH-Dependent Leaching Characteristics of Major and Toxic Elements from Red Mud

“…F − has an extremely high concentration in red mud leachate with potential environmental hazards [10,54,55]. The concentration of F − in the eluate is generally approximately 1–100 mg/L in both alkaline (pH > 12) and acidic conditions (pH < 2).…”

“…Sun et al [1] also found that the minor and trace elements, including arsenic (As, 0.2–2.0 mg/L), chromium (Cr, 0.1–5.9 mg/L), cadmium (Cd, 12–172 μg/L), mercury (Hg, 275–599 μg/L), and selenium (Se, 525–1359 μg/L), have a concentration up to 272 times higher than the maximum contamination levels (MCLs) of groundwater quality standards of both China and the US Environmental Protection Agency (USEPA). Rubinos et al [10] evaluated the leaching behavior of trace metals from red mud using batch leaching procedures, including the toxicity characteristics leaching procedure (TCLP) and sequential leaching tests. They suggested that the concentrations of Cr, copper (Cu), and nickel (Ni) exceed the regulation limits of TCLP, and the releases of Al and Cr are pH-dependent.…”

Attenuation of Cr/Pb in bauxite leachates by bentonite–polymer composite geosynthetic clay liners

“…, etc. [7][8][9][10] The pH value is as high as 12 or 13, and large amounts of heavy metal elements are dissolved, and arsenic (As), lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), chromium (Cr), and vanadium (V), [11][12][13][14] usually are at concentrations beyond groundwater quality standards in the United States and China. 6 For example, the concentration of As and Cr in bauxite leachates is 2 to 200 times higher than the maximum contaminant level (MCL) issued by the US Environmental Protection Agency.…”

Influence of feedstock type and particle size on efficiency of biochar in improving tensile crack resistance and shear strength in lean clayey soil

“…When developed stress exceeds the tensile strength of soil, crack formation starts as represented in Figure 1 (Shin and Santamarina, 2011). Desiccation cracks can promote unfavorable conditions such as water infiltration, leaches leakage, reduction in soil strength, and increased water evaporation, which can compromise environmental as well as geohazard safety (Bora et al., 2020; Bordoloi et al., 2018; Kumar et al., 2020; Sadasivam and Reddy, 2015; Zong et al., 2014). In the last few decades, attempts have been made to reduce the risk occurred due to the desiccation cracks by using innovative amendments such as natural fibers, biopolymers, waste sludge, fly ash, and biochar (Acharya et al., 2017; Bordoloi et al., 2018; Hulugalle, 1996; Kumar et al., 2020; Mei et al., 2020; Tang et al., 2012).…”

“…Other natural materials such as fibers can undergo degradation in the presence of micro-organisms in soil within 5–10 years. Similarly, fly ash, and waste sludge can also have adverse effects such as leaching due to the presence of chemical compounds within it (Goswami and Mahanta, 2007; Moriana et al., 2010; Rubinos et al., 2016). For the design period (>100 years) of man-made landfill covers biochar is a potential amendment as it has stability (i.e.…”