Pulsed electrokinetic removal of Cd and Zn from fine-grained soil

Abstract

Pulsed electrokinetics studies were carried out to optimize the removal of Zn and Cd from fine-grained soils and to observe the effects of varying the pulse frequency, pulse time ratio (on/off), and DC voltage gradient. Existing forms of heavy metals in the soil matrix were determined using a sequential extraction method. The strongly bound fraction (bound to organic matter and residuals) that is difficult to remove from the soil matrix comprised 74 and 62% of the total Zn and Cd, respectively. In the electrokinetic remediation experiments, MgSO 4 was employed to increase the ionic strength of the soil for 2 weeks. Transportation of heavy metals was influenced by the frequency, pulse ratio, and the voltage gradient of the pulsed electric field. Extraction efficiency of Zn and Cd near the anode was correlated positively with the voltage gradient at a given pulse and ratio. A high pulse frequency (1,800 cycles/h) enhanced the removal efficiency of the heavy metals compared to a low pulse frequency (1,200 cycles/h) at a supplied voltage gradient of 1 V/cm. Although pulsed electrokinetics was more effective in extracting and desorbing ions near the anode than conventional electrokinetics, its ability to transport heavy metals from the anode to the cathode was relatively small. Total removals with pulsed electrokinetics were 21-31% for Zn and 18-24% for Cd. In summary, pulsed electrokinetics can enhance removal efficiency of heavy metals and is beneficial with regard to electrical energy consumption.

Electrokinetic Treatment of Cr-, Cu-, and Zn-Contaminated Sediment: Cathode Modification

“…Additionally, the pulsed technique allows for diffusion of H + and metal ions in the sediment. These are limited during electromigration (Reddy and Saichek, 2004;Ryu et al, 2010). It has been shown that more metals desorb from sediment particles during pulsed electric field application and are therefore + depending on the amount of sorbed metal ions (Reaction 1).…”

“…To improve the heavy metal solubility, a large number of studies have been carried out (Yang and Lin, 1998;Ottosen et al, 2005;Yeung and Gu, 2011). These usually involve chemical addition in the system, but there are also those that use changes in process design to enhance metal solubility (Chung and Kamon, 2005;Chen et al, 2006;Hansen et al, 2007;Rojo and Cubillos, 2009;Rojo et al, 2010;Ryu et al, 2010;Rajić and Ugar cina Perović, 2011;Rajić et al, 2012). Besides improving the metal solubility, it is of great importance to prevent OH -ion penetration into the sediment.…”

Evaluation of Electrolyte and Electrode Spacing for Application of Electrokinetic Remediation

“…현재, 전기동력학적 정화에서 양극조와 음극 조에 전해질이나 추출액을 첨가하여 오염물의 제거효율을 높이는 방법 Kim et al, 2011a;Ryu et al, 2011), 펄스를 이용하여 오염물의 제거율을 높이고 전력소모량을 감소시키는 방법 Ryu et al, 2010), 생물학적 방법과 전기동력학적 방법을 결합한 하이브리드 공법 (Alshawabkeh et al, 1999 Table 3).…”

“…식물정화법은 처리기간이 길며 식물의 뿌리를 통 하여 중금속을 추출하기 때문에 적용 범위의 한계성을 지 니고 있다 Ryu et al, 2010). 이러 한 이유로 최근에는 점토와 같은 저투수성 토양에서도 중 금속 등의 오염물질 제거가 가능한 전기동력학적 정화기 술에 대한 연구가 활발히 이루어지고 있다 (Acar et al, 1995;Baek et al, 2007;Kim et al, 2009a;Park et al, 2009b;Ryu et al, 2009;Ryu et al, 2010;Kim et al, 2011a;Kim et al, 2012).…”

Pilot-scale ex situ electrokinetic restoration of saline greenhouse soil

“…However, these are only temporary solutions. Recently, electrokinetic (EK) treatment has been used as a method to remediate or control various contaminated media such as soils (Kim et al 2009a(Kim et al , 2009bOttosen et al 2006;Reddy and Chinthamreddy 2004;Reddy et al 2001;Ryu et al 2010;Zhou et al 2004), mine tailings Hansen et al 2005;Kim et al 2002a;Ryu et al 2009), and sludge (Kim et al 2002b;Park et al 2010). The major mechanisms responsible for the removal of contaminants in the EK treatment process are electromigration and electroosmosis (Acar and Alshawabkeh 1993;Acar et al 1995).…”