Combined adsorption/regeneration process for the removal of trace emulsified hydrocarbon contaminants

Recovery, regeneration and sustainable management of spent adsorbents from wastewater treatment streams: A review

Adsorption is the most widely adopted, effective, and reliable treatment process for the removal of inorganic and organic contaminants from wastewater. One of the major issues with the adsorption-treatment process for the removal of contaminants from wastewater streams is the recovery and sustainable management of spent adsorbents. This review focuses on the effectiveness of emerging adsorbents and how the spent adsorbents could be recovered, regenerated, and further managed through reuse or safe disposal. The critical analysis of both conventional and emerging adsorbents on organic and inorganic contaminants in wastewater systems are evaluated. The various recovery and regeneration techniques of spent adsorbents including magnetic separation, filtration, thermal desorption and decomposition, chemical desorption, supercritical fluid desorption, advanced oxidation process and microbial assisted adsorbent regeneration are discussed in detail. The current challenges for the recovery and regeneration of adsorbents and the methodologies used for solving those problems are covered. The spent adsorbents are managed through regeneration for reuse (such as soil amendment, capacitor, catalyst/catalyst support) or safe disposal involving incineration and landfilling. Sustainable management of spent adsorbents, including processes involved in the recovery and regeneration of adsorbents for reuse, is examined in the context of resource recovery and circular economy. Finally, the review ends with the current drawbacks in the recovery and management of the spent adsorbents and the future directions for the economic and environmental feasibility of the system for industrial-scale application.

Emulsified oil separation by bioadsorption: a sustainable proposal

Oil emulsions are very stable, so both the treatment and the recovery of marine oil spills require expensive technologies, sometimes inefficient. Thus, studies of alternative methods for the treatment of oily effluents and phytoremediation are very important for sustainable development. The objective of this study was to use a chemically modified biomass of Salvinia sp. (SOH), for the removal of oil from oil-in-water emulsions. Initially, a chemical modification was carried out to remove interferences and to increase the adsorption capacity of the biomass. Physicochemical characterization tests were performed to understand the structure of the adsorbent produced as well as to verify changes going on the surface of the material. Adsorption tests were done, such as concentration variation, time, temperature and pH. The maximum adsorption capacity (q_max) of SOH was obtained in 15 min and was 574.86 mg g^-1 in oil-in-salt water emulsion and 525.92 mg g^-1, for oil-in-water emulsion. The isotherm model that best fitted was Freundlich model and for the kinetic model, the best fit was obtained with the intraparticle diffusion model. Thermodynamic studies indicate that SOH has physisorption, and the process is spontaneous and reversible.

The electro-Fenton regeneration of Granular Activated Carbons: Degradation of organic contaminants and the relationship to the carbon surface

Electrochemical regeneration of Granular Activated Carbon is an emerging treatment option to restore adsorption capacity in systems designed to remove organic contaminants from aqueous solutions. The electro-Fenton process is one such electrochemical process and it is reviewed along with other members of its family including Photoelectro-Fenton and Heterogeneous electro-Fenton and electro-Fenton like reactions, for its ability to regenerate Granular Activated Carbons contaminated with organics. The behaviour of critical operating parameter such as pH, current, catalyst concentration and initial contaminant concentration are reviewed to find optimal operating conditions. The relationship between electro-Fenton regeneration and the chemical and physical surface of the carbon is also explored. Understanding regeneration mechanisms and the optimal operating conditions enables these technologies to be used commercially and to be scaled-up and treat contaminated waters more efficiently.