Effect of milling of clay on the absorption of nano-silver and investigation of its antibacterial effect in the paper

Global development and higher living standards have caused people pay more attention to health and environment. Papers such as bills and printing and writing are daily exposing to a lot of among people; hence, were to important agents in the transmission of pathogenic microorganisms. Silver-nanoparticles are including antimicrobial agents that become oxidized in the presence of oxygen and light, and their structure is unstable. They also have a strong tendency to aggregation. The structural properties of nanoclay make it the perfect choice for removing deficiencies of silver-nanoparticles. According to the electrostatic adsorption of silver nanoparticles on the surface of clay, it is expected that increasing clay surface charge as a result of mill operation, lead to increasing the absorption rate of silver.
After milling clay from, sodium boron hydride reduction method was used to deposit silver-nanoparticles on the surface of clay (milled clay). SEM images were used to evaluate the effect milling on clay dimensions and Atomic Absorption Spectrometer and Inductively coupled plasma- atomic emission spectrometry test to measure the amount of silver absorbed by the nanoclay in the production of silver-clay nanohybrid and silver-milled clay. The samples of paper were treated with both hybrids in three levels 10, 15 and 20 wt%. Antibacterial test was carried out by biophotometery. Distribution and the amount of present of nanohybrids in target papers were determined by FESEM-MAP images and elemental analysis (EDX) test.
The results showed that the amount of nanoparticles adsorbed on surface of clay was two-fold of milled clay, but during paper making because of more adsorption of silver nanoparticles on the surface of milled clay compared with the clay, that it has more absorption of pore, almost half of silver-nanoparticles were leaching. Antibacterial results obtained showed that the antibacterial properties of paper treated with both nanohybrids were high and growth rate of both types of bacteria (Escherichia coli, Bacillus subtilis and Staphylococcus aureus) significantly decreased.
According to the results of FESEM, elemental analysis and antibacterial tests could be confirmed that, silver -clay nanohybrid can be used as an appropriate antibacterial agent in the paper. Also, due to superficial absorption of silver nanoparticles on milling clay compared with original clay, is better silver- milled clay nanohybrid to be used as a coating agent on the surface of the paper, so that using less nanosilver, creates higher antibacterial effect in paper that is efficient in terms of economic and environmental problems will follow lower.