By / Ahmed Hasham
M.Sc. Analytical chemistry
Adsorption is a process in which substances transfer from gases or liquids using physical matter known as adsorbent (Worch 2012).
It is a very efficient technique to purify polluted water. Also, it is used for the removal of metal ions from aqueous solutions, adsorption proofs itself better than other. Generally, adsorption isotherm is an invaluable curve describing the phenomenon governing the retention or mobility of a substance from the aqueous phase to a solid-phase at a constant temperature and pH (Singh et al. 2016).
Adsorbent type depends on the type of water which need the adsorption technique in its treatment. As an example activated carbon is used as adsorbent in drinking water , wastewater ,industrial waste water , swimming pool and ground water while aluminum oxide and some polymers are used as adsorbent only in waste water and industrial waste water applications (Worch 2012) .
Ø Effect of pH on Adsorption
The surface characteristics of sorbents are affected by the pH value of the solution so it is a main factor in studying the effectivity of a sorbent. Most of heavy metals are cations, so the adsorbent almost anionic. At low pH range , there are further protons presented to protonate with active groups on the surface of sorbent’s so they participate with the heavy metals (Sharma, 2014) . At present, adsorption is broadly accepted in eco-friendly treatment applications all over the world. Liquid–solid adsorption techniques are based on the capability of specific solids to specially concentrate selected substances from liquid phases onto their surfaces. This principle can be used for the removal of contaminants, such as metal ions and organics, from wastewaters (Piraján and Giraldo 2012).
Modeling of adsorption procedures is vital particularly in water treatment techniques. To ensure that the suitable adsorbent is selected to remove the selected pollutant in water with respectable effectiveness, at the right percentage and in the right conditions, scientific mathematical models are employed. Furthermore, these models deliver valuable data that are valuable in developing an adsorption reactor for large-scale adsorption process (Unuabonah, et.al, 2019).
Biomass as adsorbents:
The major difficulty in wastewater and industrial wastewater treatment is the synchronized presence of many and different forms of pollutants as:
- Heavy metals.
Adsorption is the one of the most hopeful methods for waste water treatment. For economic consideration researchers had to turn their attention into lower cost adsorbents. So, a new term introduced, which is called “green adsorption”. It is meant (low-cost adsorbent derived from:
- Agricultural sources as (fruits, vegetables, foods);
- Agricultural residues and wastes;
- Low-cost sources (as activated carbons after pyrolysis / hydrothermal carbonization of agricultural sources) (Kyzas and Kostoglou 2014).
Kyzas, George Z., and Margaritis Kostoglou. 2014. “Green Adsorbents for Wastewaters: A Critical Review.” Materials. Https://doi.org/10.3390/ma7010333.
Moreno-Piraján, Juan Carlos, and Liliana Giraldo. 2012. “Heavy Metal Ions Adsorption from Wastewater Using Activated Carbon from Orange Peel.” E-Journal of Chemistry 9 (2): 926–37. Https://doi.org/10.1155/2012/383742.
Sharma, Sanjay K. 2015. Heavy Metals in Water.
Singh, Santosh Bahadur, Mahesh Kumar Gupta, Neelam Shukla, Girdhari Lal Chaurasia, Satpal Singh, and Praveen Kumar. 2016. “WATER PURIFICATION : A BRIEF REVIEW ON TOOLS AND TECHNIQUES USED IN ANALYSIS , MONITORING AND ASSESSMENT OF WATER QUALITY” 2 (2): 95–102. Https://doi.org/10.18510/gctl.2016.229.
Unuabonah, Emmanuel I., Martins O. Omorogie, and Nurudeen A. Oladoja. 2019. Modeling in Adsorption: Fundamentals and Applications. Composite Nanoadsorbents. Elsevier Inc. Https://doi.org/10.1016/b978-0-12-814132-8.00005-8.
Worch, Eckhard. 2012. Adsorption Technology in Water Treatment – Fundamentals, Processes, and Modeling.