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Green polymers as corrosion inhibitors are gradually used to protect metal in solution environment. A polyaspartic acid threonine derivative (PASP-Thr) was synthesized and its structure was characterized by Fourier transform infrared (FTIR) spectroscopy and nuclear magnetic resonance. The corrosion inhibition effect of polyaspartic acid (PASP) and PASP-Thr on carbon steel in simulated cooling water was investigated by weight loss tests and electrochemical measurements. Experimental results show PASP-Thr as a mixedtype inhibitor exhibits higher corrosion inhibition efficiency than PASP, and the inhibition efficiency of PASP-Thr reached 93.06% at the dosage was 200 mg L −1 . The carbon steel surface in different situations was analyzed using atomic force microscope, scanning electronic microscope/energy dispersive X-ray, and FTIR, demonstrates the formation of a protective film on carbon steel surface. The inhibition effect of PASP-Thr was primarily attributed to the protective film formed on steel surface by physical and chemical adsorption. Moreover, quantum chemical calculation elaborated the relationship between the inhibition efficiency and the PASP-Thr molecular structure.

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This study reports the modification of commercial cation-exchange membrane by layer-by-layer adsorption of polyethyleneimine and poly(acrylic acid) (PAA) to endow them with monovalent ion selectivity. The chemical and morphological changes of the modified membrane surface were examined by ATR-FTIR and SEM, respectively. The permselectivity for monovalent cations of the membranes was investigated by electrodialysis experiments. The effects of deposited bilayer number, the salt concentration, and pH of the dipping polyelectrolyte solutions on selectivity were investigated. Meanwhile, the resistance of membranes was measured taking energy consumption into consideration. The polyelectrolyte multilayer was crosslinked using epichlorohydrin to improve stability, and the durability of the composite membrane was studied. Separation mechanism of the composite membrane was also investigated. It is demonstrated that the bivalent cations are mainly rejected by electrostatic repulsion from the positive charge on the surface of the composite membranes. The sieving effect of the dense structure of skin layer becomes more pronounced with the number of deposited layers increased.