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Pesticides are becoming more prevalent in agriculture to protect crops and increase crop yields. However, nearly all pesticides used for this purpose reach non-target crops and remain as residues for extended periods. Contamination of soil by widespread pesticide use, as well as its toxicity to humans and other living organisms, is a global concern. This has prompted us to find solutions and develop alternative remediation technologies for sustainable management. This article reviews recent technological developments for remediating pesticides from contaminated soil, focusing on the following major points: (1) The application of various pesticide types and their properties, the sources of pesticides related to soil pollution, their transport and distribution, their fate, the impact on soil and human health, and the extrinsic and intrinsic factors that affect the remediation process are the main points of focus. (2) Sustainable pesticide degradation mechanisms and various emerging nano- and bioelectrochemical soil remediation technologies. (3) The feasible and long-term sustainable research and development approaches that are required for on-site pesticide removal from soils, as well as prospects for applying them directly in agricultural fields. In this critical analysis, we found that bioremediation technology has the potential for up to 90% pesticide removal from the soil. The complete removal of pesticides through a single biological treatment approach is still a challenging task; however, the combination of electrochemical oxidation and bioelectrochemical system approaches can achieve the complete removal of pesticides from soil. Further research is required to remove pesticides directly from soils in agricultural fields on a large-scale.

Soil contamination by petroleum hydrocarbons (PHCs) causes various acute problems such as crop growth, yield, and grain quality. Many Physico-chemical and biological approaches are employed to remove the PHCs from polluted soil. However, some of these approaches are too slow, or ineffective, and/or environmentally unfriendly. Indeed, bioelectrochemical systems (BES) combine biological methods and electrochemistry in the context of a redox reaction. BES is gaining attention from scientists and policymakers as a promising technology for the remediation of soil contaminated with PHCs. This review discusses BES working principles, mechanisms, design configuration, operational parameters, and advances in BES applications to remediate PHCs from contaminated soil efficiently. The role of biosurfactants and biochar in enhancing PHC degradation in soil using BES mediating extracellular electron transfer (EET) and biofilm formation is highlighted. Furthermore, recent innovations in this field, technical and economic challenges and limitations in scaling-up BES, and future perspectives are discussed. This review suggests that biochar-based single-chamber air-cathode reactors are preferred because of their lower cost compared to the other classic configurations. Additional efforts are needed in the design of BES reactors, soil characteristics, and seasonal variations in BES performance over a long period of operation to improve the efficiency of soil remediation and power production as well as to apply it on a large scale.

Toxic Cr(VI) polluted wastewater is worldwide recognized because of the wide application of chromium substances in various industrial sectors. Sustainable water pollution approaches are on demand now more than ever. In terms of Cr(VI), many homogenous and heterogenous techniques are applying to intensify its removal form water. Photocatalytic reduction of Cr(VI) has been suggested widely by the scientific community over the last two decades. This report addresses the current research state of the photocatalytic Cr(VI) reduction by addressing the most advances in terms of materials design and mechanistic pathways depending on the working conditions. The photocatalytic activity of different classes of materials such as single or heterojunction semiconductors, hybridization of photocatalyst nanoparticles (NPs) with sorbing materials, i.e., carbonaceous materials, metal-organic frameworks (MOFs), and conjugated polymers, is discussed in depth. The photodeposition of photoproduced Cr(III) on the surface of photocatalysts, and approaches to boost its desorption was addressed as well. The review discusses also the simultaneous photocatalytic reduction of Cr(VI) and oxidation of organic pollutants. A critical analysis of the current state and how to transfer substantial fundamental research to present world application was given by addressing the pros and cons of photocatalytic technology for Cr(VI) reduction compared to existing technologies. Positive research suggestions were provided to enhance the ability of photocatalytic technology for possible use, even for the purification of small volumes of industrial wastewater.