Removal of As(V) Based on Amino-Group Surface-Functionalized Porous Silicon Derived from Photovoltaic Silicon Cutting Powder

At a Glance

Metadata	Details
Publication Date	2021-07-15
Journal	Coatings
Authors	Kaixin Fu, Yi Li, Xiumin Chen, Wenhui Ma, Ziheng Yang
Institutions	ARC Centre of Excellence in Advanced Molecular Imaging, Yunnan University
Citations	2
Analysis	Full AI Review Included

Executive Summary

This study successfully developed a high-performance, amino-functionalized porous silicon adsorbent (TEPA-GTS-NPSi) derived entirely from photovoltaic silicon cutting waste (DWSSP).

Waste Valorization: The methodology provides a practical, high-value recycling route for Diamond Wire Saw Silicon Powder (DWSSP), transforming a major industrial waste stream into a functional material.
High Adsorption Capacity: The adsorbent achieved a maximum experimental As(V) adsorption capacity of 13.2 mg/g at room temperature and optimal pH 7, demonstrating acceptable performance compared to commercial alternatives.
Rapid Kinetics: Adsorption is fast, reaching equilibrium saturation within 60 minutes, with the initial rapid phase occurring within the first 10 minutes, beneficial for practical flow systems.
Chemical Mechanism: The adsorption process follows pseudo-second-order kinetics and the Langmuir isotherm model, indicating chemical, monolayer adsorption.
Mechanism Confirmation: DFT and XPS analyses attribute the removal mechanism to strong hydrogen bonding between the protonated amino groups (-NH₃⁺) on the adsorbent surface and the electronegative arsenic species (H₂AsO₄^-).
Excellent Reusability: The material exhibits good regeneration capability, maintaining 91.8% removal efficiency after five successive cycles using 1 mol/L HCl as the desorption agent.
Practical Application: The adsorbent effectively treated actual industrial wastewater containing arsenic, copper, and zinc, showing superior selectivity for arsenic.

Technical Specifications

Parameter	Value	Unit	Context
Raw Material	DWSSP	N/A	Photovoltaic silicon cutting waste
Adsorbent Name	TEPA-GTS-NPSi	N/A	Amino-functionalized porous silicon
Maximum Adsorption Capacity (Experimental)	13.2	mg/g	Optimized pH 7, 25 °C
Maximum Adsorption Capacity (Langmuir Model)	13.8754	mg/g	Monolayer adsorption fit (R² = 0.9782)
Optimal Adsorption pH	~7	N/A	Stable performance range (pH 4 to 8)
Adsorption Equilibrium Time	60	min	Rapid phase in first 10 min
Minimum Adsorption Limit (Residual As(V))	3	mg/L	Achieved at optimized dosage (25 mg)
Regeneration Efficiency (Cycle 5)	91.8	%	Using 1 mol/L HCl desorption agent
Grafted GTS Group Mass Loss	7.0	%	Determined by TGA
Grafted TEPA Group Mass Loss	7.1	%	Determined by TGA
Si-O-Si Bending Vibration Peak	470	cm^-1	FT-IR analysis
N1-H6 Bond Length (Adsorbed State)	1.64556	A	DFT analysis, strong H-bond indicator
Stabilization Energy E(2)	40.75	kcal/mol	NBO analysis, N atom to H-O bond interaction
As3d Binding Energy (Adsorbed)	45.2	eV	XPS analysis

Key Methodologies

The preparation of the TEPA-GTS-NPSi adsorbent involved three main stages: purification/etching, surface activation, and organic functionalization.

Silicon Powder Purification and Etching (NPSi Preparation):
- Pre-Washing: Raw DWSSP was cleaned using NH₃/H₂O₂/Deionized Water (2:2:5 ratio) for organic removal, followed by HCl/H₂O₂/Deionized Water (2:2:5 ratio) for oxide removal.
- Final Wash: A 5% HF solution wash was used to obtain purified silicon powder.
- Copper-Assisted Chemical Etching (Cu-ACE): Copper nanoparticles were deposited on the silicon surface (1 min). Etching was performed in a solution of 40% HF and 5 mM H₂O₂ for 1 hour to create nanoporous silicon (NPSi).
- Copper Removal: Residual nano-Cu particles were removed using 30% nitric acid.
Surface Activation:
- Dried NPSi was stirred for 3 hours in an H₂SO₄/H₂O₂ solution (3:1 volume ratio) to increase the density of active hydroxyl groups (Si-OH) on the surface.
Amino-Group Functionalization (TEPA-GTS-NPSi Synthesis):
- Step 1 (GTS Grafting): Activated NPSi was mixed with (3-glycidyloxypropyl) trimethoxy-silane (3-GTS) and anhydrous toluene, then refluxed at 60 °C for 24 hours to graft the silane ligand (forming GTS-NPSi).
- Step 2 (TEPA Functionalization): GTS-NPSi was reacted with Tetraethylenepentamine (TEPA) and anhydrous toluene, refluxed at 60 °C for 24 hours to introduce the terminal amino groups, yielding TEPA-GTS-NPSi.
Adsorption Studies:
- Batch adsorption experiments were conducted to optimize pH (1-8), contact time (0.5-120 min), initial As(V) concentration (10-150 mg/L), and adsorbent dosage (10-35 mg).
- Desorption and regeneration studies utilized 1 mol/L HCl solution.

Commercial Applications

This technology offers a sustainable and effective solution for heavy metal removal, particularly leveraging waste materials from the photovoltaic industry.

Industrial Wastewater Treatment:
- Nonferrous Metallurgy: Direct application in treating industrial wastewater containing high concentrations of arsenic, copper, and zinc, where the adsorbent showed high selectivity for As(V).
- Semiconductor/PV Manufacturing: Used in closed-loop water systems to purify process water, utilizing the silicon waste generated by the same industry.
Environmental Remediation:
- Groundwater and surface water purification, especially in regions affected by natural or industrial arsenic contamination, meeting requirements for low residual arsenic limits (down to 3 mg/L).
Advanced Adsorbent Manufacturing:
- Production of chemically stable, regenerable, and high-capacity porous silicon-based hybrid materials for specialized filtration cartridges and fixed-bed reactors.
Resource Management and Circular Economy:
- Implementation of industrial ecology strategies by converting high-volume, low-value silicon kerf loss into a functional, marketable product, reducing landfill burden.

View Original Abstract

In this study, amino group surface-functionalized porous silicon adsorbent was successfully prepared for the first time using diamond wire saw silicon powder (DWSSP) as raw material through copper-assisted chemical etching (Cu-ACE) and organic functional group grafting. Amino-functionalized porous silicon adsorbent (TEPA-GTS-NPSi) can be used for removing As(V) from water. The properties and mechanism of the new adsorbent were characterized by infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller analysis (BET), and thermogravimetric analysis (TGA). The concentration of metal ions in the solution was determined by inductively coupled plasma spectrometry. Meanwhile, the effects of initial pH, adsorption time, initial concentration and adsorbent dosage on the removal of As(V) in an aqueous solution were studied by intermittent adsorption experiments. The results showed that the adsorption equilibrium could be reached rapidly after 30 min soaking. Under the optimized pH of 7, the maximum adsorption capacity was 13.2 mg/g, and the minimum adsorption limit was 3 mg/L. The adsorbent shows good adsorption performance after five successive regenerated cycles. Based on the density functional theory (DFT) analysis results, the adsorption mechanism is attributed to hydrogen bond interaction between the NH2 group and As(V) ions.

Tech Support

Original Source

DOI: https://doi.org/10.3390/coatings11070850

References

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