Flux enhancement of cellulose nitrate membrane through plasma assisted route for waste and mud water treatment

Abstract

Fouling of polymeric membranes is a common problem due to its hydrophobic nature. Plasma assisted surface modification of polymeric membranes are immensely popular method in particular for the improvement of antifouling and adhesive properties. The effect of low‐pressure nitrogen plasma on surface morphology, hydrophilicity, structure, permeate flux and ageing effect for the cellulose nitrate polymer membrane are studied in the present work. The cylindrical Langmuir probe and optical emission spectroscopy are used to characterize the plasma. The macro void creation and pore enlargement effects have been observed from scanning electron microscopy images due to the surface etching of the membrane after plasma treatment. The atomic force microscopy analysis shows a prominent enhancement of the surface roughness of the plasma treated membrane. Wettability of membrane is studied as a function of plasma treatment time for treated and untreated membrane. From the contact angle measurement, it is found that the hydrophilicity of the plasma treated membranes increases with plasma treatment time. From gravity filtration process, the enhancement of permeate flux for both waste water and mud water are observed after plasma treatment. The ageing mechanism of the treated membranes is investigated for 30 days for different plasma treatment time. The hydrophobic recovery of plasma treated membranes is significant for initial ageing period of 7 days, after that it has shown almost stable in nature. A theoretical model is developed to study the hydrophilic recovery of plasma treated membranes. It is observed that the experimental results show a very good agreement with the theoretical results.

Role of plasma process gas on permeate flux augmentation of cellulose nitrate membrane for mud water treatment

“…The study reveals the distinct surface modifications as a result of the incorporation of functional groups into the plasma-treated membrane, which alter the antifouling and permeability properties of the membrane. The above investigations manifest the substantial enhancements in wettability, chemical inertness, and permeability for various polymeric membranes subsequent to cold plasma treatment 4 , 21 , 23 , 24 , 34 – 39 . The assessment of water contact angle (CA) serves as a pivotal metric for evaluating surface hydrophilicity, contingent upon surface properties like energy and roughness.…”

“…As the total oxygen and nitrogen components in the Ar plasma-treated membrane are found to be slightly higher as compared to the N 2 plasma-treated membrane, the Ar plasma-treated membrane shows a better hydrophilic nature as compared to the N 2 plasma-treated membrane. Additionally, the surface roughness also plays a vital role in water CA as well as surface hydrophilicity 1 , 24 . The increase in surface roughness in the Ar plasma-treated membrane, as compared to the N 2 plasma-treated membrane, as observed from AFM analysis, is another factor in getting better hydrophilicity in Ar plasma treatment.…”

“…The surface modification of the membrane due to plasma etching 4 , 24 plays a crucial role in removing lightweight molecular species like additives, processing aids, and adsorbed materials from the surface. The effectiveness of this phenomenon is highly dependent on the choice of operating gas used for plasma generation.…”

“…The investigation into the effects of plasma treatment on different types of the membranes such as polyacrylonitrile 23 , cellulose nitrate 24 , polyethersulfone 25 , polyacrylonitrile copolymer 26 , polysulfone 27 , polypropylene 28 , regenerated cellulose 29 , cellulose acetate composite polyion complex 30 , polycarbonate 31 , Aromatic Polyamide 32 , polytetrafluoroethylene 33 has been reported by different researchers. The study reveals the distinct surface modifications as a result of the incorporation of functional groups into the plasma-treated membrane, which alter the antifouling and permeability properties of the membrane.…”

“…The assessment of water contact angle (CA) serves as a pivotal metric for evaluating surface hydrophilicity, contingent upon surface properties like energy and roughness. In the cold plasma process, achieving the lowest water contact angle and maximal adhesion is contingent upon optimizing plasma operating conditions, including treatment time, discharge power, and process gas composition 24 , 40 .…”