Activated carbons derived from Walnut shells: Application to environmental problems

Activated carbon will be defined stating that it is an excellent adsorbent which is produced in such away that it exhibits high specific surface area and porosity. Activated carbon is one of the most commonlyused adsorbents in the removal process of industrial pollutants, organic compounds, heavy metals anddyes, among many others toxic and hazardous compounds. These characteristics, along with the surface'schemical nature (which depends on the raw materials and the activation used in its preparation process),allow it to attract and retain certain compounds in a preferential way, either in liquid or gaseous phase.Activated carbons derived from walnut shells were investigated to find the suitability of its application forremoval of pollutants from air or water streams both in the field and in industrial processes such as: Spillcleanup, Groundwater remediation, Drinking water filtration, Air purification, Volatile organiccompounds capture from painting, dry cleaning, gasoline dispensing operations, and other processes. Onthe basis of this study, walnut shell–based activated carbon was prepared by chemical activation withphosphoric acid; the influence of raw material size, activation temperature, H3PO4 concentration, and yieldof the prepared activated carbon were investigated and discussed. Results showed that, walnut shell is agood and cheap agricultural residue for the production of activated carbon, with carbon, hydrogen andnitrogen contents of 48.33, 5.511 and 0.457 % (w/w, dry basis), respectively. With an activationtemperature of 500°C, an impregnation ratio of 3:1 (v/v), and H3PO4 concentration of 85%, the activatedcarbon with better adsorption capacity and yield were 1677 mg/g and 48%, respectively. BETexperimental results indicated the potential use of walnut shell as a precursor in the activated carbonpreparation process, thus, representing an economically promising material.

Keywords:

activated carbon , adsorbent , envirmental pollutants