# Efficient Removal of Nickel from Wastewater Using Copper Sulfate–Ammonia Complex Modified Activated Carbon: Adsorption Performance and Mechanism

## TL;DR

This study shows how modifying activated carbon with a copper sulfate-ammonia complex improves its ability to remove nickel from wastewater, making the process more efficient.

## Contribution

The novel use of a copper sulfate–ammonia complex to modify activated carbon for enhanced nickel adsorption is introduced.

## Key findings

- Modified activated carbon ([Cu(NH3)4]-PAC) showed higher Ni(II) adsorption capacity than unmodified PAC.
- Adsorption mechanisms include surface complexation, cation exchange, and electrostatic interactions.
- The modified material exhibited pH buffering and adaptability, with adsorption behavior fitting the Langmuir and pseudo-second-order models.

## Abstract

The necessity to eliminate nickel (Ni) from wastewater stems from its environmental and health hazards. To enhance the Ni adsorption capacity, this research applied a copper sulfate–ammonia complex (tetraamminecopper (II) sulfate monohydrate, [Cu(NH3)4]SO4·H2O) as a modifying agent for a Phragmites australis-based activated carbon preparation. The physiochemical properties of powdered activated carbon (PAC) and a modified form ([Cu(NH3)4]-PAC) were examined by measuring their surface areas, analyzing their elemental composition, and using Boehm’s titration method. Batch experiments were conducted to investigate the impact of various factors, such as Ni(II) concentration, contact time, pH, and ionic strength, on its substance adsorption capabilities. Additionally, the adsorption mechanisms of Ni(II) onto activated carbon were elucidated via Fourier-transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The findings indicated that modified activated carbon ([Cu(NH3)4]-PAC) exhibited a lower surface area and total volume than the original activated carbon (PAC). The modification of PAC enhanced its surface’s relative oxygen and nitrogen content, indicating the incorporation of functional groups containing these elements. Furthermore, the modified activated carbon, [Cu(NH3)4]-PAC, exhibited superior adsorption capacity relative to unmodified PAC. Both adsorbents’ adsorption behaviors conformed to the Langmuir model and the pseudo-second-order kinetics model. The Ni(II) removal efficiency of PAC and [Cu(NH3)4]-PAC diminished progressively with rising ionic strength. Modified activated carbon [Cu(NH3)4]-PAC demonstrated notable pH buffering and adaptability. The adsorption mechanism for Ni(II) on activated carbon involves surface complexation, cation exchange, and electrostatic interaction. This research presents a cost-efficient preparation technique for preparing activated carbon with enhanced Ni(II) removal capabilities from wastewater and elucidates its underlying adsorption mechanisms.