Mild electrokinetic treatment of cadmium-polluted manure for improved applicability in greenhouse soil

Abstract

Applications of cadmium (Cd) and salinity-containing manures contribute to Cd pollution and salinization in greenhouse soils. In this study, chicken manure polluted with Cd (5.6 mg/kg) was mildly electrokinetically treated (0.25 V/cm) for 48 h with intermittent replacement of catholyte with 20 mM acetic acid solution to remove Cd and salinity for application without need of post-treatment in greenhouse soil. The electrokinetic treatment created pH conditions mainly ranging from 5.0 to 8.0 within the manure for minimizing re-precipitation of desorbed Cd and evaporative loss of ammonium. However, without manure pre-acidification, electrokinetic treatment resulted in negligible removal of total Cd but 61.7% of increase in the small fraction of exchangeable Cd, due to poor desorption but enhanced formation of exchangeable Cd. In contrast, manure pre-acidification with 20 mM acetic acid favored Cd desorption, leading to electrokinetic removal of exchangeable, carbonate-bound, and total Cd by 32.2%, 34.5%, and 14.5%, respectively. Mild electrokinetic treatment of manure with and without pre-acidification resulted in similar removal of salinity (72.3% and 68.0%), similar pH condition (7.2 and 7.4), and basically same evaporative loss of ammonium (14.6% and 14.2%). Overall, the mild electrokinetic treatment considerably lowered the risk of Cd and the salinity from the pre-acidified manure for improved applicability in greenhouse soil, and more studies are needed to enhance the performance of electrokinetic Cd removal from manure.

Electric Field-Enhanced Cadmium Accumulation and Photosynthesis in a Woody Ornamental Hyperaccumulator—Lonicera japonica Thunb.

“…Recently, the combination of phytoremediation and electrokinetic remediation has increasingly been used to overcome the limitations of phytoremediation and enhance remediation efficiency [27][28][29][30][31][32]. Some studies have reported that the application of electric fields could improve the bioavailability of pollutants in soils and heavy metal accumulation in plants [28,[33][34][35], and other studies investigated electric field-assisted enhancements in seed germination, plant growth, and self-organization ability under different environmental stress [36][37][38][39][40]. Nevertheless, these studies were mainly focused on crops, herbs, and aquatic plants, including lettuce, maize, tomato, ryegrass, and Canadian waterweed [41][42][43][44][45][46][47][48].…”

Remediation of Cu Contaminated Soil by Fe78Si9B13AP Permeability Reaction Barrier Combined with Electrokinetic Method

“…This method is especially suitable for the treatment of farmland soil with fine particles and high water content, which has the advantages of simplicity, low cost, and excellent effect [17,18]. Huang et al [19] used a mild electrokinetic method with a voltage gradient of 0.25 V/cm to treat cadmium-contaminated soil for 48 h, and the content of exchangeable cadmium is reduced by up to 72.3%, which effectively reduces the bioavailability of cadmium. In order to further optimize the remediation process of the electrokinetic method, some researchers proposed an electrokinetic method combined with PRB to remediate heavy metal-contaminated soil.…”