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Present study relates to the corrosivity of paper mill effluent and corrosion performance of stainless steel (SS) as a construction material for the effluent treatment plant (ETP). Accordingly, immersion test and electrochemical polarization tests were performed on SS 304 L, 316 L and duplex 2205 in paper mill effluent and synthetic effluent. This paper presents electrochemical polarization measurements, performed for the first time to the best of the authors' information, to see the influence of chlorophenols on the corrosivity of effluents. The corrosivity of the effluent was observed to increase with the decrease in pH and increase in Cl- content while the addition of SO4- tends to inhibit corrosion. Mill effluent was found to be more corrosive as compared to synthetic effluent and has been attributed to the presence of various chlorophenols. Corrosion performance of SS was observed to govern by the presence of Cr, Mo and N contents.

This study details the sonication-assisted synthesis and characterization of a cathodically deposited novel nickel-graphene oxide -zinc oxide (Ni-GO-ZnO) composite coating achieved through electrodeposition and its comparison with anodically deposited GO. This coating was comprehensively characterized using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM) coupled with Energy-dispersive X-ray spectroscopy (EDAX). Subsequently, its corrosion resistance for MS1010 mild steel in 3.5 wt % (NaCl) was evaluated via weight loss, contact angle, electrochemical impedance spectroscopy (EIS), Potentiodynamic polarization, and surface analysis techniques. These observations suggest that graphene oxide-zinc oxide (GO-ZnO) adsorbs nickel onto the MS surface effectively and reduces defects, which helps in blocking active corrosion sites. Tafel plots and EIS revealed that the Ni-GO-ZnO coating exhibited the lowest current density (39.95 µAcm²) and the highest charge transfer resistance (1211 Ωcm²). This was further validated by long-term immersion testing, where the Ni-GO-ZnO coating exhibited significantly less weight loss (1.33 mils/Y) compared to the deposited GO coating (2.2 mils/Y). The mechanism of formation of deposited GO and Ni-GO-ZnO coating on the metallic surface is proposed. The enhanced corrosion resistance of the Ni-GO-ZnO coating is attributed to its ability to 1) form a more compact metallic layer and 2) Minimize the active surface area vulnerable to corrosion attack. 3) Diminishes the presence of holes and cracks for corrosive ion ingress.4) Functionally impedes the ingress of chloride ions, primarily liable for steel degradation. The synergistic effect of the GO-ZnO constituents within the nickel matrix significantly enhances the long-term durability and integrity of the protective layer, a phenomenon hitherto unexplored. The empirical outcomes advocate for the advanced application of GO-ZnO-nickel coatings in safeguarding infrastructural materials against corrosive degradation. [Display omitted] [ABSTRACT FROM AUTHOR]

Purpose – This paper aims to report on corrosivity of secondary-stage paper mill effluent and corrosion performance of stainless steels. Design/methodology/approach – For this purpose, immersion test and electrochemical polarization tests were conducted in mill and synthetic effluent to evaluate the uniform and localized corrosion. Findings – Corrosivity of mill effluent has been compared with synthetic and primary-stage effluent of the same mill. It is observed that anions present in them, viz. SO4−, PO34−, NO2− and NO3−, impart inhibition, whereas Cl− and chlorophenols enhance the corrosivity of the effluent. The overall effect of various components was reduction in corrosivity of secondary mill effluent. Originality/value – These observations can be useful for material selection and helpful in corrosion mitigation in paper mill effluent treatment plants. [ABSTRACT FROM AUTHOR]

The paper production process comprises various manufacturing steps and generates an enormous amount of effluent, which consists of a large variety of contaminated chemicals. The higher color and chemical oxygen demand (COD) of the wastewater create a negative effect on all living forms and the natural environment. Electrocoagulation is a versatile process for the elimination of color and COD content from wastewater. In this study, the EC treatment has been used to identify the ideal conditions using several process variables such as pH, current density, time, and the dose of electrolyte. COD and color were reduced by up to 68% and 94%, respectively. Afterward, the treated water was compared with the standards of the world health organization (WHO) and the central pollution control board (CPCB) to find out the suitability of treated water for reuse for farming purposes. Germination tests of mung beans were conducted, and it was observed that the EC treated water is suitable for irrigation. The corrosion rate of mild steel was determined to be 2.85 mils/year, which has shown the short life span of mild steel electrodes. Furthermore, sludge produced by the EC process was analyzed and characterized for physicochemical analyses by using a variety of analytical techniques. The 69.93% iron content of the sludge was also recovered using the acid digestion method. After the physicochemical analyses, it was observed that sludge could also be utilized as a compelling supplement for plant growth, energy recovery, and industrial applications. According to this study, treated water could be a powerful alternative for reducing freshwater consumption in agricultural areas and increasing water availability in water-scarce areas. Effect of operating parameters on electrocoagulation treatment of pulp and paper industry wastewater, treated water and sludge management. [Display omitted] • The higher COD and color 68% and 94%, respectively, were removed from wastewater by using EC treatment. • The greater removal of pollutants occurred at a near neutral pH. • It was observed that there was an encouraging improvement in the biodegradability index of wastewater after EC process. • Treated water is found to be suitable for reuse in agriculture. • The produced sludge could be a compelling supplement for plant growth, energy recovery, and industrial applications. [ABSTRACT FROM AUTHOR]