Existence of heavy metals like zinc within water source is considered as one of the most important environmental problems. Accumulating within alive tissues, zinc raises various diseases and disorders. Chitosan is a hydrophilic polymer which is raised from acetyl groups of chitin from alkaline solution: it is employed widely as a well-known adsorbent for removing heavy metal ions. Present study aimed at optimizing the production of chitosan nano size particles by method of calvo and compared the adsorption of Zn (II) ions by chitosan macro and nano size particles. Adsorption experiments were conducted in a batch system and the effects of temperature, pH, contact time and initial concentration of metal ions on productivity of adsorption of zinc ions have been considered. Performing analysis DLS revealed that mean size of nano chitosan particles is 19.84 nm. Optimal adsorption by chitosan and nano chitosan has been done in pH 7 and about of 5. Efficiencies of both adsorbent were increased by increasing contact time. Both adsorbent had maximum efficiency at the temperature of 25°C. At the concentration of 10 mg/ L of zinc metal ions, maximum effective removal of chitosan macro and nano size particles were 90.80 and 99.10 %, respectively. Maximum capacity of adsorption by chitosan macro and nano size particle was 196.07 and 370.37 mg/g, respectively. Adsorption kinetics followed a pseudo second order model. Nanochitosan compared to chitosan particles had higher removal efficiency for Zinc metal ions due to nano size of particles, larger adsorption surfaces and more functional groups.

Nano-zerovalent iron (NZVI) was synthesized using green tea (GT) extract and it was used as an adsorbent in arsenate removal from water. FESEM, PSD, and XRD employed in the examination of particles and their characterizations. Results showed that the particles were spherical lumped together in a texture structure with sizes ranging from 20 to 70 nanometers. All experiments were accomplished in a batch mode. Adsorption isotherm, adsorption kinetics, and the effects of pH, GT-NZVI dosage, and ultrasonic wave power on arsenate separation capabilities were explored. The results suggested that the arsenate removal efficiency enhanced with increasing GT-NZVI dosage. Increase in pH from 3 to approximately 6 leads to increase in the removal efficiency; however, increasing the pH further decreased the removal efficiency. The effect of ultrasonic power on As(V) removal was dependent on pH and NZVI dosages. The positive effect was more pronounced at low adsorbent dosages and acidic solution in which the As(V) removal efficiency improved with increasing ultrasonic power. However, in highly alkali solutions As(V) removal efficiency reduced with increasing ultrasonic power. The adsorption kinetics followed second order, while the adsorption isotherm was fitted best with Langmuir equation at a maximum capacity of 34.2 mg g−1.

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