Effect of Chloride Ions on Electro-Coagulation to Treat Industrial Wastewater Containing Cu and Ni

Integration of sequential electrocoagulation and adsorption for effective removal of colour and total organic carbon in textile effluents and its utilization for seed germination and irrigation

Textile effluent discharge can negatively impact the environment and living organisms due to its potential toxicity, higher percentages of total organic carbon (TOC) contents, and so on. The study investigates the extraordinary performance of the electrocoagulation process (ECP) combined with powdered activated carbon (PAC) as a highly effective and environmental friendly method of treating textile effluents. This scientific work mainly includes the focus on removing toxic components in textile effluents, such as high concentrations of colour and TOC using synthesized PAC derived from coconut shells coupled with the ECP (ECP-PAC). Initially, PAC was characterized by using XRD, Raman, BET, FTIR, and TGA studies. Subsequently, the pilot-scale ECP-PAC batch reactor was constructed with iron (Fe) as an anode and copper (Cu) as a cathode. The pilot-scale ECP-PAC batch reactor has achieved higher treatment efficiency in a shorter reaction time with low energy consumption compared to a stand-alone ECP. Further, the optimum conditions for effective ECP-PAC have been optimized, such as pH 7.5, applied current density (0-50 mA/cm2), reaction time (0-30 min), electrode combinations (Fe-Cu) with electrode distances of 5 cm apart, and an optimum dose of 5 g/L of PAC. Specifically, 98% of the colour and 96% of the TOC contents present in the industrial textile effluent were treated in 15 and 30 min, respectively. In quantitative perspectives, the developed batch reactor has sharply decreased TOC (324.1 mg/L), IC (1410 mg/L) and TC (1019 mg/L) to 13.55 mg/L (96%), 31.49 mg/L (97%), and 48.05 mg/L (95%), respectively, in 30 min demonstrating its sensitivity and selectivity with the utmost care. Moreover, the physicochemical properties of the treated water were convincingly assessed. That is, it remains suitable for the seed germination of mung bean and chlorophyll content study. Thus, the developed methodology could effectively reduce freshwater consumption in the agricultural sector, increase freshwater availability in water-scarce regions, and facilitate the increase of the recharging capacity of groundwater tables.

Description of a Fe/Al Electrocoagulation Method Powered by a Photovoltaic System, for the (Pre-)Treatment of Municipal Wastewater of a Small Community in Northern Greece

Small and insular communities are sometimes not served by an efficient Wastewater Treatment Plant, and this is a hazard for both the environment and public health. A wastewater treatment apparatus based on the electrocoagulation process (EC) was tested with municipal wastewater from a small community in Northern Greece with a maximum of 6500 population equivalents. COD decrease was assessed under various parameters: current intensity, time duration, pH and use of Fe or Al electrodes. A simulation of meeting the community’s electricity needs with this apparatus was tested through RETScreen software. The results showed a satisfactory COD decrease through electrocoagulation which was affected by all the parameters mentioned; Fe electrodes could efficiently be used at 300 mA for 60 min for 55% COD removal. It was also shown that a photovoltaic panel system covers the electricity needs of the apparatus, thus no external electricity source is needed for its use. This apparatus could be used effectively by this community, so that the running costs are minimal.

The Effect of Fe(II), Fe(III), Al(III), Ca(II) and Mg(II) on Electrocoagulation of As(V)

The interaction between metal chlorides and electrocoagulation was tested. Precipitation of As(V) was found to be optimal at pH 4.9 using FeCl2, 2.6 for FeCl3, 3.8 using AlCl3, 11.6 using CaCl2 and 8.6 using MgCl2. As(V) removal through electrocoagulation went down as initial pH (pHi) of the solution increased. Addition of FeCl2 increased removal of As(V) at all pHi but was not able to achieve full removal at pHi 7. FeCl3 had a similar effect but a lower Fe(III) concentration of 30 mg/L was not sufficient for full removal at pHi 5 either. AlCl3 addition reduced removal efficiency at pHi 3 but removed all or most As(V) through precipitation at pHi 5 and 7, with complete removal followed through electrocoagulation. The addition of CaCl2 and MgCl2 resulted in nearly identical behavior. Addition of either at pHi 3 had no influence, but at pHi 5 and 7 caused complete removal to take place.

New biomaterials for Ni biosorption turned into catalysts for Suzuki-Miyaura cross coupling of aryl iodides in green conditions

In parallel with increasing Ni production and utilisation, Ni pollution in the soil–water continuum has become an alarming and global problem. Solutions for removing Ni from industrial effluents have been widely investigated and biosorption has emerged as an efficient, cost-effective, scalable and sustainable alternative for water treatment. However, the biosorption capacity is limited by the chemical composition of the biomaterial and the Ni-enriched biomaterials are rarely valorised. In this work, the biosorption capacity of three abundant biomaterials with different chemical properties – water hyacinth, coffee grounds and pinecones – was studied before and after functionalization, and reached a maximum biosorption capacity of 51 mg g⁻¹ of Ni(ii). A bioinspired functionalization approach was investigated introducing carboxylate moieties and was conducted in green conditions. The Ni-enriched biomaterials were valorised by transformation into catalysts, which were characterised by MP-AES and XRPD. Their characterisation revealed a structure similar to nickel formate, and hence the Eco-Ni(HCOO)₂ catalysts were tested in Suzuki–Miyaura reactions. Several aryl iodides were successfully cross-coupled to phenylboronic acids using Eco-Ni(HCOO)₂ without any ligand, a mild and green base in a mixture of green solvents.

New biomaterials were functionalised for biosorption of Ni from aqueous solutions and valorised as ecocatalysts in Suzuki–Miyaura green reactions.