Using solar cell to phytoremediate field-scale metal polluted soil assisted by electric field

Lead dissociation and redistribution properties of actual contaminated farmland soil after long-term EKAPR treatment

Electrokinetic-assisted phytoremediation (EKAPR) is a potential technology much affected by the metal species and accessibility to plant roots. In this study, Pb-contaminated red soil was remediated with Sedum plumbizincicola to investigate the changes in soil pH, available nutrients, dissociation and redistribution of Pb under a long-term periodic reversal direct-current electric field. This approach could effectively activate soil P, K, organic matter (OM) and Pb, without significant soil acidification; the effect was positively correlated with applied voltage. Soil Pb can be continuously dissociated, migrated, and tended to accumulate in the middle region. The maximum Pb removal rate in the anodic section of the EKAPR system was 21.4%, and the aggregation rate in middle regions was 14.4%, higher than the available Pb content of the original soil. The Pb desorption in aqueous solution increased significantly with increasing voltage, irrespective of the solution pH. At a voltage of 20 V, the Pb cumulative desorption content reached 91.1 mg kg-1 (pH = 7), which was 2.7 times than that without electric field (33.2 mg kg-1). Compared to original soil (2.80 mg kg-1) and the control (14.54 mg kg-1), the available Pb in the anode section of EKAPR system (20.66 mg kg-1) increased by 637.9% and 42.1%, respectively. These results indicated that except for the indirect influence of soil pH changes, electrodynamics can directly promote the bioavailability and dissociation of Pb at the soil-water interface. This finding provides a new perspective for further studies on the mechanism of Pb speciation evolution and accumulation changes using EKAPR.

Emerging electrochemistry-based process for sludge treatment and resources recovery: A review

The electrochemical process is gaining widespread interest as an emerging alternative for sludge treatment. Its potentials for sludge stabilization and resources recovery have been well proven to date. Despite the high effectiveness of the electrochemical process having been highlighted in several studies, concerns about the electrochemical sludge treatment, including energy consumption, scale-up feasibility, and electrode stability, have not yet been addressed. The present paper critically reviews the versatile uses of the electrochemical processes for sludge treatment and resource recovery, from the fundamentals to the practical applications. Particularly considered are the enhancement of the digestion of the anaerobic sludge and dewaterability, removal of pathogens and heavy metals, and control of sludge malodor. In addition, the opportunities and challenges of the sludge-based resource recovery (i.e., nitrogen, phosphorus, and volatile fatty acids) are discussed. Insights into the working mechanisms (e.g., electroporation, electrokinetics and electrooxidation) of electrochemical processes are reviewed, and perspectives and future research directions are proposed. This work is expected to provide an in-depth understanding and broaden the potential applications of electrochemical processes for sludge treatment and resource recovery.

Heavy Metal Pollutions: State of the Art and Innovation in Phytoremediation

Mineral nutrition of plants greatly depends on both environmental conditions, particularly of soils, and the genetic background of the plant itself. Being sessile, plants adopted a range of strategies for sensing and responding to nutrient availability to optimize development and growth, as well as to protect their metabolisms from heavy metal toxicity. Such mechanisms, together with the soil environment, meaning the soil microorganisms and their interaction with plant roots, have been extensively studied with the goal of exploiting them to reclaim polluted lands; this approach, defined phytoremediation, will be the subject of this review. The main aspects and innovations in this field are considered, in particular with respect to the selection of efficient plant genotypes, the application of improved cultural strategies, and the symbiotic interaction with soil microorganisms, to manage heavy metal polluted soils.