Separating Rubber From Sand

Background

There are various components that come into play when constructing the ideal athletic field. But what happens after the game is over? Our most recent solution comes from a company specializing in recycling sports field turf to explore the potential for repurposing its materials in residential areas. One of the primary materials to be recycled is the rubber infill used on the turf. To accomplish this, the rubber must be cleaned and separated from the sand present in the turf. This means separating the rubber from sand and other materials.

The first step in this process involved conducting a sieve analysis to determine the distribution of materials across various size ranges.

Initial Mesh Analysis

The sieve analysis results are summarized below:

Opening (Microns) Mesh Weight Retained (g) % Retained
2380 8 21.3 4.16%
1000 18 366.3 71.54%
500 35 102.3 19.98%
250 60 17.6 3.44%
125 120 1.4 0.27%
74 200 0.5 0.10%
PAN 2.6 0.51%
TOTAL 512  

Findings:

  • Large rocks were retained primarily over the 8 mesh (2380 microns).
  • The rubber was concentrated between the 8 mesh and 18 mesh (1000 microns).
  • Cuts below the 18 mesh primarily consisted of sand.

Initial Screening Process

The samples were then run through a screening unit using Mesh 8 and Mesh 18. This process effectively separated oversized and undersized materials. The remaining material was collected for further processing using a Stoner for separation.

Opening (Microns) Mesh Weight Retained (g) % Retained
2380 8 1560 9.70%
1000 18 12360 76.87%
PAN 2160 13.43%
TOTAL 16080  

Post-Stoner Analysis

After passing the on-size product through the Stoner, a mesh analysis was performed with finer cuts between Mesh 8 and Mesh 18 to verify if any sand had passed into the lighter fraction.

Opening (Microns) Mesh Weight Retained (g) % Retained
2380 8 0.1 0.05%
1680 12 41.5 21.85%
1410 14 68.8 36.23%
1190 16 37.2 19.59%
1000 18 19.4 10.22%
841 20 13 6.85%
PAN 9.9 5.21%
TOTAL 189.9  

Observations:

  • A small number of sand granules were identified in the bottom pan, though the quantity was minimal and required close inspection to confirm.
  • Some white granules initially thought to be sand were determined to be a mix of rubber, plastic, and possibly organic materials (e.g., grass or paper). These particles share a similar density to rubber, making them difficult to separate through gravity-based methods.

Conclusion

The initial analysis and screening process successfully separated the oversized and undersized materials, providing valuable insight into the composition of the rubber and sand fractions. The following gravity separation process conducted on the Stoner was highly effective, with minimal sand contamination detected in the final product.