A Gold Rush: Designing Hydrogels for Selective Recovery in Wastewater Containing Mixed Metal Ions
Pamela Cinfrignini1,2, Alice Boschetti1,3, Giacomo Ghini4
1European Laboratory for Non-Linear Spectroscopy (LENS), Via Nello Carrara 1, 50019 Sesto Fiorentino, Italy.
ACS Applied Materials & Interfaces
|November 25, 2024
Summary
This study introduces poly(acrylamide-co-acrylic acid) hydrogels for efficient gold recovery from industrial wastewater. These novel adsorbents selectively capture and reduce gold, offering a sustainable solution for precious metal recycling.
Area of Science:
- Materials Science
- Environmental Science
- Chemical Engineering
Background:
- Synthetic hydrogels offer scalable solutions for wastewater treatment.
- Effective removal and recovery of heavy metals, especially gold, are critical for environmental protection and resource recycling.
- Existing gold recovery methods often rely on weak interactions or complex formations, necessitating alternative approaches.
Purpose of the Study:
- To develop and evaluate easy-to-make poly(acrylamide-co-acrylic acid) hydrogels for selective gold recovery.
- To investigate the hydrogels' ability to reduce gold cations into elemental nanoparticles and microparticles.
- To assess the hydrogels' performance in complex industrial wastewater matrices containing other precious metals.
Main Methods:
- Synthesis of poly(acrylamide-co-acrylic acid) hydrogels.
- Batch adsorption tests to determine gold adsorption capacity.
- Analysis of gold reduction into elemental forms (nanoparticles and microparticles).
- Competitive adsorption studies with other precious metal ions (Ru, Ir, Pd, Pt, Rh).
Main Results:
- The hydrogels demonstrated a high adsorption capacity for gold, reaching up to 124 mg/g.
- Selective separation of gold from other precious metal ions was achieved.
- Gold cations were successfully reduced to elemental gold nanoparticles and microparticles.
- The process operates effectively in acidic environments at room temperature.
Conclusions:
- Poly(acrylamide-co-acrylic acid) hydrogels are effective and selective adsorbents for gold recovery from industrial wastewater.
- This method provides a novel route for gold recovery via reduction, avoiding complexation or weak interactions.
- The hydrogels show potential for recovering gold from diverse complex metal solutions, including electronic waste leachates.
Related Concept Videos
00:56Extraction: Advanced Methods
420
Metal ions can be separated from one another by complexation with organic ligands–the chelating agent– to form uncharged chelates. Here, the chelating agent must contain hydrophobic groups and behave as a weak acid, losing a proton to bind with the metal. Since most organic ligands used in this process are insoluble or undergo oxidation in the aqueous phase, the chelating agent is initially added to the organic phase and extracted into the aqueous phase. The metal-ligand complex is...
420
01:06Coagulation
271
Colloidal solids are solid particles suspended in solution. They are usually negatively charged, attracting a compact primary layer of positively charged ions, which attract more counterions to form an electrical double layer. Electrostatic repulsion between the charged double layers prevents the particles from colliding, stabilizing the colloids. These solids are often undesirable because they can contain toxins that are difficult to remove. Coagulation is a technique that helps aggregate and...
271
01:17Precipitation and Co-precipitation
1.7K
Precipitation and coprecipitation methods can be used to separate a mixture of ions in a solution. In qualitative inorganic analysis, ions that form sparingly soluble precipitates with the same reagent are separated based on the differences in solubility products. For example, consider the separation of Cu(II) and Fe(II) ions by precipitation as insoluble sulfides. First, copper(II) sulfide is precipitated by the addition of acidic H2S, where the dissociation of H2S is suppressed. Adding H2S...
1.7K
01:19Masking and Demasking Agents
2.3K
EDTA titrations may necessitate masking and demasking agents to temporarily protect a particular metal ion in a mixture from the EDTA reaction. These agents facilitate the sequential analysis of the metal ions by forming stable complexes with some—but not all—metal ions during certain steps.
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on...
There are many masking agents, such as cyanide, fluoride, triethanolamine, thiourea, and 2,3-bis(sulfanyl)propan-1-ol (formerly 2,3-dimercapto-1-propanol), with the masking agent chosen based on...
2.3K
01:08Electrodeposition
603
Electrodeposition is a technique used to separate an analyte from interferents by electrochemical processes. Here, the analyte is a metal ion that can be deposited on an electrode immersed in the sample solution. The electrochemical setup consists of an anode and a cathode. When an electric current is applied to the setup, oxidation occurs at the anode. At the cathode, which consists of a large metal surface, metal ions undergo reduction and deposit onto the surface.
Electrodeposition can...
Electrodeposition can...
603
03:46Qualitative Analysis
22.0K
For solutions containing mixtures of different cations, the identity of each cation can be determined by qualitative analysis. This technique involves a series of selective precipitations with different chemical reagents, each reaction producing a characteristic precipitate for a specific group of cations. Metal ions within a group are further separated by varying the pH, heating the mixture to redissolve a precipitate, or adding other reagents to form complex ions.
For instance, group IV...
For instance, group IV...
22.0K