Removal of copper oxide nanoparticles from aquatic mediums by coagulation-ultrafiltration membrane hybrid continuous system

Abstract

The overall aim of this work is to investigate the fundamental mechanisms and phenomena governing the removal of engineered nanomaterials in aquatic systems, specifically, copper oxide nanoparticles (CuO NPs) which are expected to have a huge impact in the field of nanotechnology and its applications. Nanofiltration membranes (NF) are very effective in removing nanoscale pollutants. However, high pressures (100–1,000 psi) are required to operate NF membranes. Also, the NF membrane technique is not preferred for use in the treatment of wastewater containing nanoscale particles due to the fouling of membrane problem which results in decreasing treated water production. Conversely, ultrafiltration membranes (UF) require much lower pressures (5–60 psi) and the fouling problem is reduced, but unfortunately, they are not effective in retaining dissolved ions, organic solutes, and nanoscale pollutants. Therefore, in the present study, we used the coagula-tion/flocculation/sedimentation (CFS) step as a pre-treatment process to enhance the UF process. Experimental work was carried out to investigate the effects of solution chemistry (i.e., pH values, suspended solids concentrations, and turbidity of solution) and the physio-chemistry characteristics of nanomaterials, e.g., shape, size, electrostatic charge on the particles surface and the composition of nano-materials on the removal process, select the suitable kind of coagulants; viz., Magnafloc LT31 as anionic, Magnaafloc 10 as cationic or Dynafloc 30 as inorganic polymers and their optimum doses related to the efficiency of CFS processes in the different cases and finally, study the effect of design considerations of CFS systems and operating parameters of the filtration system such as trans-mem-brane pressure as a function of treated water fluxes and effect of backwashing and chemical cleaning on the membrane fouling and consequently determine their effects on the filtration performance. The removal efficiency of nano-materials and the efficiency of turbidity removal varied according to the coagulant type. The results indicated that the efficiency of CuO NPs removal was 87.4%, 89.33%, and 90.3% in case of CFS process, it was found 94.2%, 97%, and 97.66% in case of CFS/UF process; followed the following order for different types of coagulant, Magnafloc LT31 > Dynafloc 30 > Ma gnaafloc 10. The efficiency of turbidity removal for the CFS process was estimated at 81.7%, 91.0% and 90.0% with Magnafloc 10), Dynafloc 30 and Magnafloc LT31; respectively. Similar to the CFS process, the CFS/UF process indicated that the efficiency of turbidity removal was observed greater than 96% using Magnafloc L31 while 94.3% in the case of Dynafloc 30 and recorded 87.9% only with Magnafloc. That is meaning that the efficiency of turbidity removal and nanoparticle removal in both CFS and CFS/UF processes was more efficient using anionic and inorganic polymers as a coagulant.