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This research article presents an in situ electrosynthesis of aluminum hydroxides by anodic dissolution of sacrificial aluminum anode and their application towards the adsorption of herbicide 2-(2,4dichlorophenoxy)propanoic acid (2,4-DP) from aqueous solution. Different sacrificial anode material like iron, magnesium, zinc and aluminum are tested and stainless steel is used as the cathode. The optimization of different experimental parameters like current density, pH, temperature and interelectrode distance on the adsorption of 2,4-DP was carried out. The results showed that the maximum removal efficiency of 93.0% was achieved with aluminum as sacrificial anode at a current density of 0.10 A dm À2 and pH of 7.0. The adsorption of 2,4-DP preferably followed the Langmuir adsorption isotherm. The adsorption kinetic studies showed that the adsorption of 2,4-DP was best described using the second-order kinetic model. Thermodynamic parameters indicates that the adsorption of 2,4-DP on aluminum hydroxides was feasible, spontaneous and endothermic.

The magnesium hydroxide generated in the cell removes the copper present in the water, reducing the copper concentration to less than 1 mg/L, making it safe for drinking. The results of the scale-up study show that the process was technologically feasible.

A batch adsorption process was applied to investigate the removal of manganese from aqueous solution by oxidized multiwalled carbon nanotubes (MWCNTs). In doing so, the thermodynamic, adsorption isotherm, and kinetic studies were also carried out. MWCNT with 5-10-nm outer diameter, surface area of 40-600 m(2)/g, and purity above 95 % was used as an adsorbent. A systematic study of the adsorption process was performed by varying pH, ionic strength, and temperature. Manganese-adsorbed MWCNT was characterized by Raman, FTIR, X-ray diffraction, XPS, SEM, and TEM. The adsorption efficiency could reach 96.82 %, suggesting that MWCNT is an excellent adsorbent for manganese removal from water. The results indicate that second-order kinetics model was well suitable to model the kinetic adsorption of manganese. Equilibrium data were well described by the typical Langmuir adsorption isotherm. Thermodynamic studies revealed that the adsorption reaction was spontaneous and endothermic process. The experimental results showed that MWCNT is an excellent manganese adsorbent. The MWCNTs removed the manganese present in the water and reduced it to a permissible level making it drinkable.

The environmental friendly and cost-effective few-layered graphene nanosheets (GNs) are identified as superior adsorbent for chlorophenoxyacetic acid herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), 2-(2,4-dichlorophenoxy) propanoic acid (2,4-DP), 4-chloro-2-methylphenoxyacetic acid (MCPA), 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2-(2-methyl-4chlorophenoxy) propionic acid (MCPP) from an aqueous solution. The effects of pH, ionic strength and temperature on the adsorption of herbicides were explored. The prepared GNs showed the maximum removal efficiencies of 82, 80, 86, 82 and 70% for 2,4-D, 2,4-DP, 2,4,5-T, MCPA and MCPP respectively. The results revealed that the adsorption follows a pseudo-secondorder kinetics model and confirms the Langmuir adsorption isotherm. From the thermodynamic parameters, it is suggested that the adsorption of herbicides on GNs follows the endothermic and spontaneous processes. The results show that the electrochemically prepared GNs will be considered the suitable material for water purification in the near future.