Cd Adsorption by Chemically Activated Tropical Peat

Author(s)

Lima, Jacqueline Zanin ; Raimondi, Isabela Monici ; Silvestre Rodrigues, Valeria Guimaraes ; LopezAcosta, NP ; MartinezHernandez, E ; EspinosaSantiago, AL ; MendozaPromotor, JA ; Lopez, AO

• Document type: Journal article
• Source: GEOTECHNICAL ENGINEERING IN THE XXI CENTURY: LESSONS LEARNED AND FUTURE CHALLENGES; v. N/A, p. 9-pg., 2019-01-01.

Abstract

Soil contamination with cadmium is a global problem, in particular, in abandoned mine areas, and remediation techniques using peat have been investigated to reduce the environmental impact. Peat, a natural and low-cost material, is a universal adsorbent effective in treatment processes for the removal of contaminants from the water and soil. Various chemical pre-treatments can be applied to remove metallic cations by activating the adsorption properties of peat. In this study, the physicochemical characteristics and the performance of Cd(II) adsorption using treated Brazilian peat (with HCl) were evaluated. Batch test results were fit to mathematical models for the prediction of adsorption isotherms. A comparison of the more-popular linear forms depict good correlations with the experimental data. When the activated peat (pH = 4.0) was assessed, the correlation coefficient for the linearized Freundlich isotherm (0.9271) was higher than two different linear equations of Langmuir models (Langmuir-1 = 0.9158; and Langmuir-2 = 0.9101). Similarly, in the case of the activated peat (pH = 4.5), the correlation coefficient for the linearized Freundlich isotherm (0.9622) is also higher than two different Langmuir models (Langmuir-1 = 0.9433; and Langmuir-2 = 0.9243). The activated peat (pH = 4.5) had a higher overall adsorption capacity than the activated peat (pH = 4.0). The removal capacity increased from 0.8879 to 3.8481 mg g(-1) and 0.944 to 4.176 mg g(-1) in the activated peats (pH of 4.0 and 4.5, respectively), with an increase in initial Cd(II) concentration from 20 to 160 mg g(-1). Moreover, the use of human bioaccessibility experiments was assessed in order to define the Cd amount that is readily available for human uptake, post-adsorption in peat. The experimental values for human bioaccessibility increased with the increase of adsorbed concentration and the Cd concentrations were higher in the first stage of the extraction for all peat samples. The study shows that activated peat is a potential adsorbent for Cd(II). Despite that, further research is needed to explore the specific mechanisms of contaminant-peat adsorption and desorption over time, including the competition with other metallic ions and the environmental impact in real conditions during soil remediation. (AU)

• FAPESP's process: 15/02529-4 - Geological-geotechnical characterization of reactive organic materials to be used in the retention of potentially toxic metals
• Grantee: Jacqueline Zanin Lima
• Support Opportunities: Scholarships in Brazil - Master
• FAPESP's process: 17/16961-0 - Use of organic compost and peat in the retention of Pb, Zn and Cd and evaluation of the possible availability, toxicity and bioaccessibility of these metals after retention
• Grantee: Jacqueline Zanin Lima
• Support Opportunities: Scholarships in Brazil - Doctorate