Recovering Zinc from electroplating wastewater by crystallization in a pellet reactor

A pellet reactor (PR) was used to investigate the ability for zinc recovery from electroplating wastewater. The pellet reactor is a fluidized bed reactor, in which the nucleated precipitation of heavy metals occurred on the surface of seeding material. The zinc removal efficiency was 75% at molar ratio [CO3 2-]/[Zn2+] of 2.5, the flowrate of 16 L/h, sand’s diameter of 0.25 – 0.5 mm, and sand’s mass of 50 g. The elemental analysis of zinc carbonate and zinc hydroxide crystallization was analyzed by X-ray energy dispersive spectrometer (EDS) and the surface was characterised by Scanning electron microscope (SEM) to get the morphological observation of the pellets after 38-day operation. This study demonstrated that the fluidized bed reactor can be considered a feasible method for zinc removal efficiency from electroplating wastewater to achieve sustainable development.

Zinc removal from highly acidic and sulfate-rich wastewater in horizontal sub-surface constructed wetland

This study demonstrated the successful utilization of a lab-scale baffled horizontal constructed wetland substituted with mixed organic media for zinc removal from high acidity (∼610 mg L−1 as CaCO3) sulfate-rich (∼1,300 mg L−1) wastewater. The wetland was planted with Typha latifolia. The mean zinc concentration in the influent was gradually increased from 0.56 ± 0.02 mg L−1 to 5.3 ± 0.42 mg L−1. The mean zinc concentration in the outflow was 0.22 ± 0.19 mg L−1, accounting 95% zinc removal throughout the study. However, total zinc uptake by plants was 533 mg kg−1, accounting for only 1.2% of total zinc removal and therefore, major zinc retention occurred within wetland media (83%). The overall activity and specific sulfidogenic activity decreased at the end of the study to 1.43 mg COD removed mg TVS−1 d−1 and 0.60 mg sulfate reduced mg TVS−1 d−1, respectively. Additionally, 16S rRNA sequencing revealed major dominant phyla present: Firmicutes (36%), Proteobacteria (16%), Actinobacteria (8.8%), Planctomycetes (7.8%), Chloroflexi (3.5%), Acidobacteria (1.9%) and Fibrobacteres (1.5%).

Preparing Modified Activated Carbon from Cassia Fistula Seed with HNO3 for Zinc Removal in Wastewater

The economic’s development also bring urbanization and industrialization in many countries. However, many pollutants are also discharged into the environment, especially heavy metals (Zinc) seriously affects people's life and health as well as the water environment. This study reports on the preparation of activated carbon materials modified with HNO3 from Cassia Fistula seed for heavy metal removal. The results showed that zinc removal efficiencies were 65.06%; 72.19%; 75.64%; 78.57% corresponds to concentrations of 50, 30, 20, 10 ppm at optimal survey conditions pH 5, dosage of 0.3 g/50ml and 60 minutes processing time. The research results show that the activated carbon modified with HNO3 from Cassia Fistula seed is a promising absorption material for heavy metal removal in wastewater.