Comparative Investigation of Bio and Mineral Absorbents on Water Salinity Reduction

Available water resources are limited, thus use of saline water can protect water resources and compensated water scarcity. Since saline water cannot be used directly, this study investigated the adsorption capacity of Zeolite, Perlite as minerals and rice husk and seashell as bio compounds in water solution.

Particles were classified in five different sizes of 841, 400, 177, 125 and 74 µm which based on ASTM sieves. Sodium chloride solution was prepared in different concentration of 25, 50, 100, 200, 300, 500, 750, 1000, 3000, 5000, 7000 and 10000 ppm.  The effects of the sizes, dosage, contact time, rate of mixing with duration of 10, 15, 25, 35, 45, 60 and 120 minutes for the salt removal done with batch experiments in 25oC. In this method the sodium chloride solution with certain amounts of adsorbent put on a shaker device with constant speed of 200 rpm and were mixed at intervals of 10, 15, 25, 35, 45, 60 and 120 minutes. Then the samples in centrifuged with 10000 rpm in 10 minute and the upper solution used for chloride titration.

The effects of different amount of absorbent on salt absorbance showed that for all samples the highest absorbance is related to the range of 2 grams. Among the used sizes of particles, the most efficiency was related to the size of 74 µm in salt absorption. The optimum time of used samples was identified as 25, 15, 25 and 15 min for zeolite, perlite, rice husk and sea shell respectively. Based on isotherm model, perlite and rice husk followed Langmuir model, while zeolite and seashell followed Freundlich.

Mineral and bio sorbents in different micron sizes have able to absorb salt ions. Among the use of different adsorbents, zeolite showed highest efficiency to salt adsorption.