Study on highly efficient Cr(VI) removal from wastewater by sinusoidal alternating current coagulation.

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Electrochemistry

Background:

• Hexavalent chromium (Cr(VI)) poses significant environmental and health risks due to water pollution.
• Electrocoagulation (EC) is effective for wastewater treatment but often suffers from high energy consumption.
• Direct current coagulation (DCC) faces challenges with energy demands and electrode passivation.

Purpose of the Study:

• To introduce and evaluate sinusoidal alternating current coagulation (SACC) for efficient Cr(VI) removal.
• To reduce energy consumption and electrode loss in wastewater treatment.
• To optimize SACC parameters using response surface methodology (RSM).

Main Methods:

• Investigated the effects of pH, current density, initial Cr(VI) concentration, and reaction time.
• Employed response surface methodology (RSM) for process optimization.
• Analyzed coagulation properties using SEM, EDS, FTIR, and XRD; applied Langmuir isotherm and second-order kinetic models.

Main Results:

• SACC significantly reduced concentration polarization and prevented electrode passivation, lowering energy consumption by 14.98% and electrode loss by 16.4% compared to DCC.
• Achieved 99.73% Cr(VI) removal from wastewater (33.1 mg·dm⁻³ initial concentration) at pH 5.6, 2.7 A·m⁻², for 20.5 min, with residual Cr(VI) <0.1 mg·dm⁻³.
• SACC-generated coagulants exhibited larger specific surface area and enhanced adsorption performance, with Cr(VI) removal fitting Langmuir and second-order kinetic models.

Conclusions:

• SACC is a highly efficient and energy-saving technique for removing Cr(VI) from wastewater.
• The method offers improved coagulation properties and effective Cr(VI) adsorption.
• SACC presents a viable alternative to conventional EC methods for industrial wastewater treatment.