Forward osmosis (FO) is a low-energy treatment process driven by osmosis to induce the separation of water from dissolved solutes/foulants through the membrane in hydraulic pressure absence while retaining all of these materials on the other side. All these advantages make it an alternative process to reduce the disadvantages of traditional desalination processes. However, several critical fundamentals still require more attention for understanding them, most notably the synthesis of novel membranes that offer a support layer with high flux and an active layer with high water permeability and solute rejection from both solutions at the same time, and a novel draw solution which provides low solute flux, high water flux, and easy regeneration. This work reviews the fundamentals controlling the FO process performance such as the role of the active layer and substrate and advances in the modification of FO membranes utilizing nanomaterials. Then, other aspects that affect the performance of FO are further summarized, including types of draw solutions and the role of operating conditions. Finally, challenges associated with the FO process, such as concentration polarization (CP), membrane fouling, and reverse solute diffusion (RSD) were analyzed by defining their causes and how to mitigate them. Moreover, factors affecting the energy consumption of the FO system were discussed and compared with reverse osmosis (RO). This review will provide in-depth details about FO technology, the issues it faces, and potential solutions to those issues to help the scientific researcher facilitate a full understanding of FO technology.

The method of creating various nanoparticles (NPs) using different metals or metal ions and plant extracts is regarded as an environmentally friendly method in nanotechnology as an alternative to physical and chemical methods. NPs, when made through green synthesis, have a wide range of applications in agriculture, biomedical, and environmental sciences because they use fewer harmful chemicals. This review presents the principles and methods for green synthesis of NPs, as well as a comprehensive study of NP synthesis from plants and their recent applications. Plant extracts with low environmental toxicity, including magnesium oxide, zinc oxide, silver, and gold, were used to synthesise NP.