The growing scarcity of fresh water has motivated the use of non-conventional and re-used water resources for agriculture by applying some efficient technologies. The desalination technologies for agricultural irrigation play a major role in satisfying growing water demands in water scarce regions. Due to stringent ionic concentration standards for agricultural irrigation water, desalination for agriculture is more energy demanding and additional post-treatment is requisite. Reverse osmosis (RO) has emerged as an efficient technology, but the burning of fossil fuels to fulfil the energy requirements is becoming expensive and emission of greenhouse gases is recognized as harmful to the environment. Thus, efforts should be directed towards cost reduction by integrating renewable energy resources into the process. Many of the bench and pilot scale trials like integrated RO with low energy such as forward osmosis (FO), nanofiltration (NF), microfiltration (MF) and solar energy revealed significant improvements in cost savings. However, all these modern technologies have their own problems which can be overcome by further research and development. This paper aims to review the main benefits and constraints associated with desalination technologies for agriculture. The available water resources, the desired qualities of water for agriculture and the challenges and future of desalination in agriculture are discussed.

A simple approach is demonstrated for the preparation of a charged active layer of a thin film composite nanofiltration (TFC-NF) membrane using two liquid phases (triethylamine, TEA, and trimesoyl chloride, TMC) over an ultrafiltration support. The thickness of the active layer formed can be varied in the range of 100–500 nm by varying the composition of TEA (0.25–1.5 wt%) while maintaining a fixed composition of TMC at 0.1 wt%. The chemistry of the active layer was confirmed using Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. Further morphological and physical properties of the TFC-NF membrane were characterized using field emission scanning electron microscopy, atomic force microscopy, a zeta potential analyzer, a contact angle goniometer, and molecular weight cut-off studies. The membrane chemical stability was proven over a wide pH range of 3–12. The membrane surface showed the highest negative charge compared to any of the commercially available NF membranes. The permeability of the TFC-NF membrane to seawater was 1.4 L m⁻² h⁻¹ bar⁻¹ with a greater rejection of monovalent ions than any of the commercially available NF membranes. Remarkably, the TFC membrane showed a high selectivity towards seawater boron separation with a rejection value of 40% at seawater pH, which is approximately three times higher than the best tight layered commercially available NF90 membrane.

The separation of toxic boron from seawater using nanofiltration (NF) membrane technology is challenging due to the neutral charge associated with boric acid at seawater pH. In this study, the ethylenediamine functionalized Graphene oxide (EDA-GO) derivative is utilized as a nanofiller to coat the active top layer of the NF membrane over the polyethersulfone ultrafiltration support. The coating involved a self-assembly reaction of hydrolyzed trimesic acid (TMA) molecules facilitated by a triethylamine base. The unique hypothesis for coating enabled the –NH2 of EDA-GO to interact with the –COOH of TMA via hydrogen bonding interactions. The rejection shown by the M-0.05 membrane with 0.05wt% loading of EDA-GO towards MgSO4, Na2SO4, and NaCl was >98%, >97%, and 63%, respectively. The same membrane produced water flux in the range of 35-37 L/m2h with the modest significance of the salts on the membrane flux. The M-0.05 membrane showed significantly higher rejection towards boron (>47%) with a flux of 16.7 L/m2h for the beachwell seawater feed owing to the repulsive interaction between the borate ions and -NH2 and -OH groups. The rejection and flux offered by the M-0.05 membrane towards seawater's monovalent and divalent constituents were much higher than the commercial NF-90 and NF-270.