An organoclay formula for the slow release of soluble compounds

• A general formula for slow-release of chemicals
• Organoclay and chemicals are mixed and pressed to make pellets.
• Release rate is adjustable by changing pellet size.

Slow-release formulations have been developed to enhance the effective use of active ingredients. In the case of fertilizers the formulations reduce nutrient leaching and greenhouse gas emissions. While polymer-coating is the dominant technology in producing slow-release fertilizers there is a demand for alternative options for different usages. To this end, a commercially available organoclay, with a basal spacing of 3.67 nm, was used as matrix to produce pellets of CuSO4 and dicyandiamide (DCD) of different sizes by a die set and hand press. Both CuSO4 and DCD pellets showed a good slow-release performance in dissolution tests. Large pellets (1.2 cm in diameter) of CuSO4 had a better performance in slow-release than small ones (0.7 cm). For DCD pellets (0.7 cm in diameter) it took 6 days for a complete dissolution. The slow-release effect is probably due to the hydrophobic nature and high aspect ratio of the organoclay. The former makes soluble compounds between organoclay particles less susceptible to dissolution in water, whereas the latter hinders the dissolution of solutes inside a pellet by making their diffusion passage tortuous. The organoclay formulation is easy to make, and the rate of solute release can be adjusted by changing pellet size.