Agricultural by-product extracts as scale inhibitors of mild steel in tap water

Abstract

Three industry by-products, namely rapeseed pomace from the wastes of edible oil production, sugar beet pulp from the wastes of sugar production and fodder radish cake, have been tested as scale inhibitors of mild steel in tap water. 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). 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. 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.