AGRICULTURAL BY-PRODUCT EXTRACTS AS SCALE INHIBITORS OF MILD STEEL IN TAP WATER

Abstract

Background. In industrial heating processes, scaling is a major problem especially when natural water is used as heat carrier. The world economic losses due to scaling are estimated to constitute billions of dollars per year, the development of efficient, environmentally friendly and cheap approaches for reduction of scaling is an actual task nowadays. Utilization of agro-food wastes as a renewable source of scale inhibitors for water treatment of cooling water systems is a promising alternative to the existing approaches. Objective. Three industry by-products, namely rapeseed pomace, sugar beet pulp and fodder radish cake, have been tested as scale inhibitors of mild steel in tap water. Methods. Ethanol extracts were prepared by maceration and the electrochemical approach to study the scale formation was utilized, based on the measurement of oxygen reduction current during nucleation and formation of calcium carbonate in the presence of extracts. Scaling time, porosity and area density of the scale was determined and used to characterize the inhibition efficiency. Chemical compositions of extracts were analysed by GC-MS analysis (gas chromatography with mass selective detector by mass selective integration). Results. The rapeseed pomace extract and fodder radish cake extract at the concentration of 10 mL/L appeared to be efficient scaling inhibitors. Sugar beet pulp extract increases the crystallization time, however the amount of deposited scale appeared to be the same as in the tap water. Conclusions. The scale inhibition is caused mainly by the formation of adsorbed film on the scale nucleus that blocks the surface and prevent further crystal growth. Natural extracts are a promising source of scale inhibitors due to their low price, efficiency and environmental safety.

Keywords

• scale inhibitors
• mild steel
• green inhibitor
• scaling time