Silicon Extraction from a Diamond Wire Saw Silicon Slurry with Flotation and the Flotation Interface Behavior

At a Glance

Metadata	Details
Publication Date	2024-12-15
Journal	Molecules
Authors	Lin Zhu, Dandan Wu, Shicong Yang, Keqiang Xie, Kuixian Wei
Institutions	Yunnan University, Kunming University of Science and Technology
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Silicon Extraction from DWSSS via Flotation

This document analyzes the research concerning the efficient extraction of high-purity silicon from Diamond Wire Saw Silicon Slurry (DWSSS) using flotation, focusing on the interface behavior of the Dodecylamine (DDA) collector. This analysis highlights 6CCVD’s capabilities in supplying high-specification MPCVD diamond materials (SCD, PCD, BDD) essential for advanced research in PV material recycling, surface chemistry, and process optimization.

Executive Summary

This study successfully demonstrates an efficient, high-recovery method for recycling 6N grade silicon waste generated during diamond wire sawing (DWSSS) using flotation.

Maximal Recovery Achieved: Silicon recovery reached a maximal value of 98.2% under optimal conditions.
Optimal Parameters: The highest recovery was achieved using a Dodecylamine (DDA) dosage of 0.6 g·L^-1 at the natural slurry pH (4-5).
Kinetics: The flotation process follows a first-order kinetics model and achieves high recovery within a short processing cycle (24 minutes).
Mechanism Confirmation: DDA acts as an effective collector by spontaneously adsorbing onto the silicon surface, confirmed by Density Functional Theory (DFT) calculations.
Surface Modification: Adsorption of DDA significantly increases the silicon particle hydrophobicity (contact angle > 90°), enhancing floatability.
Industry Impact: This method offers a sustainable, low-contamination route for high-value silicon resource recovery, avoiding the metal impurity reintroduction common in traditional lengthy recovery processes.

Technical Specifications

The following hard data points were extracted from the experimental results and computational analysis:

Parameter	Value	Unit	Context
Maximal Silicon Recovery ($\epsilon$)	98.2	%	Optimal DDA dosage (0.6 g·L^-1)
Optimal DDA Dosage	0.6	g·L^-1	At natural pH (4-5)
Optimal Slurry pH Range	4-5	N/A	Natural pH after DDA acetate addition
Flotation Time for Maximal Recovery	24	min	Total flotation duration
Flotation Rate Constant (k)	0.506	N/A	Highest constant achieved (at pH 5, 0.6 g·L^-1 DDA)
Average Silicon Particle Size (DWSSS)	0.52	µm	Fine particle size requiring precise surface control
Adsorption Energy ($\Delta E$)	-3.28	eV	DFT calculation for DDA adsorption on Si (111)
Silicon Contact Angle (Post-DDA)	> 90	°	Indicating significant hydrophobicity increase
Surface RMS Roughness (Rq, Post-DDA)	207	nm	Increased from 123 nm (DWSSS only)
Impeller Speed	1920	r·min^-1	Flotation machine operating parameter

Key Methodologies

The silicon extraction and interface behavior analysis relied on precise control of chemical and physical parameters, supported by advanced characterization and computational modeling:

Slurry Preparation: 400 mL of original DWSSS was placed in a 500 mL flotation cell and diluted to 500 mL total volume.
Mixing and Conditioning: The impeller speed was set at 1920 r·min^-1. The slurry was stirred for 2 minutes, followed by the addition of the DDA collector (and kerosene co-collector) and stirring for an additional 3 minutes.
Flotation Process: Air was pumped into the cell at a flow rate of 200-300 L/h. Concentrates were collected by scraping the froth every five seconds for a total flotation time of 24 minutes.
Recovery Calculation: Recovered silicon concentrate and tailings were filtered, dried at 80 °C, and weighed to calculate silicon recovery using the mass balance equation.
Surface Characterization:
- Zeta Potential: Measured using a Malvern ZEN-3700 analyzer to assess surface charge variation with pH and DDA interaction.
- Contact Angle: Tested using a Krüss K100 surface tension meter to quantify hydrophobicity changes.
- Morphology: Analyzed via Atomic Force Microscopy (AFM, Bruker Dimension Icon) and Scanning Electron Microscopy (SEM-EDS, ZEISS Gemini 300) to observe roughness and elemental composition changes post-adsorption.
Computational Modeling (DFT): Adsorption location and energy were calculated using the Adsorption Locator module (COMPASS II force field) and CASTEP module (BFGS optimization, GGA, PBE functional, Tkatchenko-Scheffler DFT-D3 dispersion correction) on a Si (111) crystal plane model.

6CCVD Solutions & Capabilities

The successful recycling of high-purity silicon relies heavily on understanding and controlling surface chemistry, crystal structure, and material purity—core competencies of 6CCVD. Our MPCVD diamond materials are perfectly suited to replicate, extend, and industrialize the fundamental research presented in this paper, particularly in developing robust sensors and high-ppurity processing equipment.

Research Requirement / Application	6CCVD Material Solution	Customization Potential & Value Proposition
High-Purity Material Baseline	Optical Grade Single Crystal Diamond (SCD)	Our SCD offers exceptional purity, ideal for fundamental studies of surface adsorption mechanisms (like DDA on Si) where material contamination must be strictly avoided. Available in thicknesses from 0.1 µm to 500 µm.
Interface Adsorption Studies (Si (111) Focus)	Custom SCD Wafers on Specific Orientations	The DFT analysis utilized the Si (111) plane. 6CCVD can supply SCD grown on precisely oriented substrates, ensuring the crystalline quality necessary for advanced surface science and interface modeling replication.
Electrochemical Flotation Monitoring	Heavy Boron-Doped Diamond (BDD)	BDD is the premier electrode material for harsh chemical environments (like flotation slurries). We provide highly conductive BDD plates and substrates (up to 10mm thick) for developing robust, chemically inert zeta potential sensors or electrochemical monitoring systems.
Advanced Surface Characterization	Ultra-Low Roughness PCD and SCD	The paper relies on AFM/SEM to measure roughness (Ra, Rq). 6CCVD guarantees superior polishing: Ra < 1nm for SCD and Ra < 5nm for inch-size PCD, providing the controlled surfaces required for accurate micro-scale analysis of adsorption layers.
Scaling and Equipment Integration	Large-Area Polycrystalline Diamond (PCD)	We offer custom PCD plates and wafers up to 125mm in diameter, suitable for scaling up industrial PV waste recovery processes or integrating large diamond components into pilot flotation cells.
Custom Sensor Integration	In-House Metalization Services	For integrating diamond materials into sensors or electrodes, 6CCVD provides internal metalization capabilities, including Au, Pt, Pd, Ti, W, and Cu layers, allowing researchers to specify complex contact geometries (e.g., Ti/Pt/Au stacks).

Engineering Support

6CCVD’s in-house team of PhD material scientists specializes in diamond surface chemistry, electronic properties, and custom fabrication. We offer expert consultation to assist engineers and scientists in selecting the optimal diamond material specifications (purity, doping, orientation, and metalization) for projects related to PV waste recovery, advanced flotation chemistry, and high-purity material processing.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Diamond wire saw silicon slurry (DWSSS) is a waste resource produced during the process of solar-grade silicon wafer preparation with diamond wire sawing. The DWSSS contains 6N grade high-purity silicon and offers a promising resource for high-purity silicon recycling. The current process for silicon extraction recovery from DWSSS presents the disadvantages of lower recovery and secondary pollution. This study focuses on the original DWSSS as the target and proposes flotation for efficiently extracting silicon. The experimental results indicate that the maximal recovery of silicon reached 98.2% under the condition of a dodecylamine (DDA) dosage of 0.6 g·L−1 and natural pH conditions within 24 min, and the flotation conforms to the first-order rate model. Moreover, the mechanism of the interface behavior between DWSSS and DDA revealed that DDA is adsorbed on the surface of silicon though adsorption, and the floatability of silicon is improved. The DFT calculation indicates that DDA can be spontaneously adsorbed with the silicon. The present study demonstrates that flotation is an efficient method for extracting silicon from DWSSS and provides an available option for silicon recovery.

Tech Support

Original Source

DOI: https://doi.org/10.3390/molecules29245916

References

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2022 - Review of resource and recycling of silicon powder from diamond-wire sawing silicon waste [Crossref]
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2020 - Occurrence State and Dissolution Mechanism of Metallic Impurities in Diamond Wire Saw Silicon Powder [Crossref]