Sorption is an effective, reliable, and environmentally friendly treatment process for the removal of phosphorus from wastewater sources which otherwise can cause eutrophication of receiving waters. Phosphorus in wastewater, if economically recovered, can partly overcome the future scarcity of phosphorus resulting from exhaustion of natural phosphate rock reserves. The authors present a comprehensive and critical review of the literature on the effectiveness of a number of sorbents, especially some novel ones that have recently emerged, in removing and recovering phosphate. Mechanisms and thermodynamics of sorption, as well as regeneration of sorbents for reuse using acids, bases, and salts, are critically examined.

Cadmium (Cd) is an environmental pollutant that can be readily taken up by plants and may enter the food chain, causing risk to human health. It can also affect soil quality and, if easily leached, has the potential to pollute surface and ground waters. Sorption and desorption are critical processes controlling the phytoavailability and mobility of Cd in soils. The authors present the present knowledge on the mechanisms and hysteresis of Cd sorption and desorption in soils and factors such as pH, ionic strength, index cation, other heavy metal cations, inorganic anions, organic ligands, Cd loading rate, and the type and amounts of organic matter and inorganic colloids influencing these processes. The methods used to determine the nature and magnitude of Cd sorption and desorption are also critically reviewed.

Forward osmosis (FO) is one of the emerging membrane technologies which has gained renewed interest recently as a low energy desalination process. The central to FO process is the draw solution (DS) and the membrane because both play a substantial role on its performance. Hence, the selection of an appropriate DS is crucial for the process efficiency. Many DS have been tested so far for a wide range of modern applications and this paper aims to review the various aspects of the DS in the process performance and provides valuable information regarding the selection criteria of suitable DS. Several general DS properties such as the osmotic pressure and the water solubility can affect the process performance. Other intrinsic properties to specific novel DS such as the emerging magnetic nanoparticles (MNPs) can also have an impact on the process efficiency and have to be evaluated. Separation and recovery of the DS are one of the major challenges facing the development of FO process. The recovery process should not be energy intensive, otherwise the FO process cannot be comparable with other pressure-driven processes. Thermolytic solutions such as ammonia carbonates are considered as the promising DS for desalination applications; however, their recovery process efficiency relies on the availability of low-grade heat. MNPs are emerging and effective DS for desalination and can be readily recovered by a magnetic field or conventional membrane processes. However, the aggregation of MNPs due to their magnetic properties has been issued. The vast numbers of studies on the use of NaCl as DS for the treatment of impaired water open up the possibilities of using seawater or reverse osmosis brine streams as suitable DS for such purpose. Fertilisers were also suggested as DS for seawater and wastewater treatment when the diluted DS can be used directly for irrigation. The development of an adequate and efficient DS coupled with a low-cost energy recovery system is crucial to the performance of the process and to achieve success for the large scale of FO.