Impact of barium and cadmium on defluoridation by calcite: batch reactor and column tests

Cai, Qianqian; Turner, Brett D.; Sheng, Daichao; Sloan, Scott

Title: Impact of barium and cadmium on defluoridation by calcite: batch reactor and column tests
Creator: Cai, Qianqian; Turner, Brett D.; Sheng, Daichao; Sloan, Scott
Relation: Funding BodyARCGrant NumberLP100200488 http://purl.org/au-research/grants/arc/LP100200488
Relation: Environmental Engineering Science Vol. 34, Issue 11, p. 792-804
Publisher Link: http://dx.doi.org/10.1089/ees.2017.0006
Publisher: Mary Ann Liebert
Resource Type: journal article
Date: 2017
Description: This study focuses on the investigation regarding impact of Ba²⁺ and Cd²⁺ on defluoridation by calcite because Spent Pot Lining (SPL, a byproduct generated during the aluminum production) leachate is a complex chemical cocktail. To better understand defluoridation processes and replicate the situation in the field, column tests were conducted. Results indicate that presence of neither Ba²⁺ nor Cd²⁺ has significant impact on fluoride retention when compared with the blank (no metals) because the relative concentration values (F/F_o) as well as the transport parameters like retardation factor (R_c) and distribution coefficient (K_d) are almost the same. PHREEQC, a geochemical software, was then applied to simulate the column test processes (i.e., 1D reactive/transport processes) based on the mechanism of CaF₂ precipitation followed after calcium dissolution. As indicated in the batch reactor test, addition of Cd²⁺ may inhibit calcite dissolution; therefore, a new phase "CalciteSupp" (a phase representing the suppressed solubility of calcite) was defined. Modeling results exhibit good predictions of observed data, and the log_k solubility of the hypothetical "CalciteSupp" equilibrium phase implies the suppression of calcite dissolution in the metal samples. Moreover, saturation indices obtained by modeling indicate the precipitation of CdCO₃ and BaCO₃, revealing that addition of metals may influence fluoride removal at some point during the process, but has no big impact on overall defluoridation. The initial development of the PHREEQC geochemical model presented shows potential in being able to be used as a predictive tool for the design of fluoride remediation strategies, such as permeable reactive barriers, and transport parameters obtained on the basis of the column tests, and CXTFIT (a computer program for evaluating and estimating transport parameters) modeling can be applied in practical design.
Subject: calcite; column test; CXTFIT; fluoride removal; hill model; PHREEQC
Identifier: http://hdl.handle.net/1959.13/1394337
Identifier: uon:33682
Identifier: ISSN:1092-8758
Language: eng
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