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This comprehensive review highlighted how the expired drugs manage corrosion reactions on metal/alloy surfaces, especially types of carbon/mild steel, Sabic iron, copper, and aluminium in NaCl or acid solution. Several types of expired drugs and the optimum conditions presented in this review were summarized from relevant studies. The performance of expired drugs which covers inhibition efficiency, inhibition mechanisms, and metal surface analysis was informed. The contribution of the chemical composition, molecular structure, compatible treatment conditions, and some corrosion analysis methods were mentioned. Current challenges and future prospects were also discussed for further investigations and developments to obtain superior inhibitors and save the environment.

The high concentration of cyanide in Dioscorea hispida dennst should be reduced through immersion in seawater and interaction with rubbing ash. Soaking seawater prepared in immersion time 12, 24, and 36 hours accompanied by the replacement of seawater every three hours, while interaction with rubbing ash was ready with 75% and 100% concentration of ash on 12, 24, and 36 hours of storage time respectively. Measurement of cyanide concentrations of Dioscorea hispida dennst samples was prepared by argentometry titration with Liebig method after through the steam distillation process. Based on the results of this study, it found that immersion time for 12, 24, and 36 hours could reduce cyanide concentrations about 48.30%, 64.44%, and 70.88%, respectively. The interaction by using 75% rubbing ash for 12, 24, and 36 hours, it can reduce 24.09%, 38.69%, and 51.42% cyanide concentration in Dioscorea hispida dennst tubers, respectively. The Dioscorea hispida dennst tubers smeared with100% rubbing ash for 12, 24, and 36 hours. It can reduce cyanide content in Dioscorea hispida dennst by 36.26%, 49.92%, and 59.63%, respectively. Further treatment with drying and fermentation produces Dioscorea hispida dennst with a lower concentration of cyanide about 88.68% with a soft and white texture.

Methylene blue (MB) is a dye in wastewater from textile industries that pollutes the water environment. Reduction of its content is necessary for protecting humans and the surrounding environment. This study fabricated chitosan/Fe3O4 nanocomposite through the mixture of chitosan from crab shell waste and magnetite (Fe3O4) from local sand iron with sodium tripolyphosphate (STPP)-sulfate crosslinker as an adsorbent to reduce methylene blue content. The obtained composite was characterized by Fourier Transform Infrared (FTIR) Spectrophotometer and X-Ray Diffraction (XRD) instrument. The contents of methylene blue before and after applying adsorbent-based nanocomposite were determined using an ultraviolet-visible (UV-Vis) spectrophotometer. FTIR characterization results show that chitosan and chitosan/Fe3O4 nanocomposite had successfully synthesized based on the typical vibrational peaks. The deacetylation degree of chitosan was 69.79%. Fe3O4, and chitosan/Fe3O4 nanocomposite, were confirmed by XRD patterns. The chitosan/Fe3O4 nanocomposite adsorption capacity reached 45.37 mg/g when adsorption occurred with 20 mg adsorbent, pH 9, and contact time of 1.5 h. Hence, the chitosan/Fe3O4 nanocomposite in this study has potency and is applicable to adsorb MB effectively.

The presence of salts and dissolved gas like CO2 that is carried with natural gas and crude oil along the pipeline is the main reason for corrosion and scale formation. These problems are usually resolved separately by corrosion inhibitors and scale inhibitors or acidification. Meanwhile, utilizing a compound to resolve both corrosion and scale formation has an advantage in the economic side and working time. N,O-carboxymethyl chitosan or N,O-CMCs is one of the chitosan's derivates. It is water-soluble and has different functional groups. Those properties support its capability as a complexing agent on corrosion and scale inhibitors. Synthesis of N,O-CMCs was carried out by chemical reactions between chitosan and chloroacetic acid under alkaline circumstances. N,O-CMCs product was characterized using FT-IR and 1H-NMR spectroscopy. The inhibition efficiency was analyzed by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The measurements showed that the highest efficiency of corrosion inhibition reached 63.54% when the concentration and temperature were 30 ppm and 35 °C, respectively. N,O-CMCs was classified as a mixed-type inhibitor. The adsorption mechanism of the inhibitor followed Langmuir adsorption isotherm. The static scale inhibition test informed that the optimum inhibition efficiency of N,O-CMCs reached 60.00%.