Adsorption modelling and fixed-bed column study on milk processing industry wastewater treatment using chitosan zinc-oxide nano-adsorbent-coated sand filter bed

This study aims to develop a chitosan-zinc oxide nano-adsorbent-coated sand (CZOCS) filter bed for getting rid of milk processing industry wastewater (MPIW) in a safe way. Chitosan zinc oxide nano-adsorbent (CZnO) of 88.35 +/- 2.89 d.nm size was used to coat naturally available sand through a calcination process at 200 ? for a heating rate of 5 ?/min. The characteristics of the diffraction peaks and functional groups are attributed to the nature of CZnO loading on the sand surface. The increase in breakthrough and exhaustion times is caused by the biological oxygen demand (BOD) and chemical oxygen demand (COD) of influent having more time to interact with the adsorbent as bed height increases, resulting in higher reduction efficiencies. Lower bed heights (10 cm) which saturate faster than higher bed heights (40 cm) result in a shorter mass transfer time. Adsorption capacity at the 95% column exhaustion point increased from 611.04 to 1089.63 mg/g for BOD and from 4512.29 to 5600.81 mg/g for COD. Different kinds of kinetic models have been used to forecast breakthrough curves employing experimental data. Statistical and error function parameters were used to choose the best-fit model. Among the models investigated, the Thomas model was shown to be the best-fit with the highest R-square values of 0.9942 and 0.9939. The CZOCS has high reusability and could be used for up to six cycles of organic pollutant adsorption. Aside from that, novel CZOCS could be used to clean real MPIW, and making it one of the most promising adsorbents.

Automated summary

This study aims to develop a chitosan-zinc oxide nano-adsorbent-coated sand (CZOCS) filter bed for safe treatment of milk processing industry wastewater (MPIW). The CZOCS showed higher reduction efficiencies with increased bed height due to longer interaction time between influent and adsorbent. The adsorption capacity of CZOCS increased at the 95% column exhaustion point for BOD and COD, and the adsorbent exhibited high reusability.