Investigating the Use of Waste Hemp Derived Biochar Adsorbents for Contaminants in Oil

Crystallization and precipitation of minerals (Ca²⁺, Ba²⁺, CO₃^2-, SO₄^2- etc.) present in water can cause organic scaling, which directly interferes with oil and gas production, impedes fluid flow, and adds costs due to treatment and removal processes. Scaling also obstructs the contact between metal and corrosion inhibitor, intensifying local corrosion of pipes. Therefore, it is important to reduce if not eliminate scale formation in pipelines. Our overall goal is to find a more cost effective and environmentally friendly way to prevent this issue by using different carbon-based adsorbents to remove scaling ions, in particular Ca²⁺. The in-house prepared adsorbents tested were: Base Coke, Coke Hemp 1, Coke Hemp 2, Hemp 1, Activated Hemp 1, Cellulose 300, Activated Cellulose 300, Hemp 2, Activated Hemp 2, and Refluxed Hemp 2. As preliminary work, different Ca²⁺ concentration solutions ranging from 10-50 ppm were prepared and 24-hour adsorption tests were set for each of the adsorbents. A Flame Atomic Absorption Spectrometer (FAAS) was used to analyze and detect the Ca²⁺ ions in the solutions. After 24 hours, the adsorbents were separated from the solution which was then analyzed using FAAS to determine the amount adsorbed. While analyzing the Ca²⁺ results, it was found that activated cellulose and cellulose biochar gave the best results for Ca²⁺ adsorption. While hemp on its own (whether as biochar or activated) is not very successful in trapping the calcium, when mixed with coke, it successfully adsorbed Ca²⁺. To gain an understanding of these results, it was decided, in the first instance, to look at the ash content of the bio-adsorbents. Coke and cellulose had negligible ash content (<1%) which aided in the adsorption process of calcium, but hemp biochars had a very high ash content (23-60%). It is suspected that the high ash content of hemp is due to the growth environment (soil, fertilizers added) and the ash may be blocking effective adsorption sites. Thus, an acid reflux was set up to see if the ash content of hemp biochar could be lowered to improve the adsorption of calcium.