Wastewater treatment using Mg-doped ZnO nano-semiconductors: A study of their potential use in environmental remediation

Structural, morphological, optical, and photocatalytic properties of Mg-doped ZnO nano-semiconductors were investigated. All nanostructures exhibited spherical morphology with average crystallite diameters and band gap energy values between 47-54 nm and 3.00-3.05 eV, respectively. The increase in Mg ion contents (0.1-1.0 mol %) enhanced the photocatalytic activity of the nano-semiconductors for decontamination of non-treated laundry wastewater, degrading approximately 53% of pollutants (with absorption at lambda = 290 nm) after 240 min of UV-vis irradiation. The best photocatalytic efficiency exhibited by ZnO-Mg 1.0% is probably associated to an increase in the amount of oxygen vacancies (V-O) and consequent reduction in the recombination rate of electron-hole (e-h) pairs. The treatment of laundry wastewater also demonstrated reduction of 31% in total organic carbon (TOC), improvement in the biodegradability of the contaminants, and a high efficacy in wastewater disinfection. In addition, the treated laundry wastewater promoted a germination rate of cucumber seeds equivalent to the observed rate for the control. Phytotoxicity of treated wastewater on tomato roots reduced about 73%, indicating that the treated laundry wastewater does not essentially need to be disposed into water bodies. Instead, it may be reused as irrigation water. Interestingly, Mg-doped ZnO nano-semiconductors did not cause damage to normal and healthy fibroblast cells, demonstrating their potential to be used in environmental remediation, considering the low-cost, non-toxicity, and high efficiency of these nanomaterials.

Automated summary

The Mg-doped ZnO nano-semiconductors showed improved photocatalytic activity for degrading pollutants in untreated laundry wastewater. The increase in Mg ion contents enhanced photocatalytic efficiency by promoting oxygen vacancies and reducing recombination rates of electron-hole pairs. Additionally, the treated wastewater exhibited reduced phytotoxicity and could potentially be reused for irrigation due to the non-toxicity and high efficiency of the nanomaterials.