REVERSE OSMOSIS (Syllabus: GS Paper 3 – Sci and Tech)

News-CRUX-10     23rd March 2024        
output themes

Context: Reverse osmosis (RO) water purifiers are gaining popularity in India as a preferred option for ensuring safe and clean drinking water. Nevertheless, experts caution that RO water, which may contain dangerously low mineral levels, can adversely affect health.

Reverse Osmosis

  • About: It is a water purification process employing a partially permeable membrane to eliminate ions, undesirable molecules, and larger particles from drinking water.
  • Principle of Reverse Osmosis: Reverse osmosis operates by reversing the mechanism of osmosis, employing pressure against a salt solution and a semi-permeable membrane.
  • Mechanism: High-pressure pumps force water across the RO membrane, leaving behind 95% to 99% of dissolved salts in the reject stream.
  • Application of Pressure:In reverse osmosis, the salt solution is pressurized against the semi-permeable membrane, surpassing the osmotic pressure.
  • Pressure Dependency: The pressure needed correlates with the salt concentration; higher concentrations demand higher pressures.
  • Selective Rejection: Contaminants are rejected based on size and charge, enhancing purification effectiveness.
  • Industrial Applications: RO is crucial for producing demineralized water, vital for various industrial processes.


  • About: Diffusion entails the transfer of particles or energy from areas of high concentration to regions of lower concentration.
  • Scope: It applies to various entities such as atoms, ions, molecules, and even energy itself.
  • Gradient Dependency: The driving force behind diffusion is the gradient in Gibbs free energy or chemical potential.