Efficiency of Magnetic Granular Adsorbent Based on Natural Zeolite/Chitosan in Removing Arsenic from Polluted Water

Hypothesis: 

Among the various pollutants found in natural water, the heavy metal arsenic is more important due to its high toxicity. One of the most efficient methods to remove this pollution from water streams is the surface adsorption method. Zeolite nanocomposites can be considered powerful among arsenic adsorbers. Powder adsorbents are not very effective in industrial systems due to the problems such as clogging of filters, high pressure drop and also the problem of separation from water.

To solve this problem, zeolite nanocomposite powder was transformed into beads using the chitosan gel method in three different types of cross-linking solutions including sodium hydroxide, sodium tripolyphosphate and joint sodium hydroxide/sodium tripolyphosphate. The effect of various parameters such as the type and initial ratio of the materials on the formation of beads was investigated.

The results showed that the beads formed in the sodium hydroxide+sodium tripolyphosphate cross-linking solution and the optimal initial ratio of 1:3 from chitosan to the nanocomposite have a more suitable appearance and strength and better performance in arsenic absorption. In order to confirm and justify the mentioned Findings, SEM, BET and AAS analyses were performed. Operational parameters of initial arsenic concentration and adsorbent dose which are effective on the beads’ adsorption efficiency were investigated and the optimal amount of adsorbent dose was determined as 1 g/L with an efficiency of 92.9%. In order to obtain more information about the method of adsorption and determining the maximum capacity of adsorbents, Langmuir and Freundlich isotherms for granular adsorbents were investigated. The highest adsorption capacity of 7450.7 mg/g was obtained and Freundlich isotherm was in better agreement with the results.