Utilization of Pulse Processing Waste (Cajanus cajan Husk) for Developing Metal Adsorbent: A Value-added Exploitation of Food Industry Waste

摘要

India is the largest producer of pulses (edible legume) in the world. Pigeon pea or Tur (Cajanus cajan) is the second most major pulse produced in India and is mainly processed to convert into product known as “Tur dal”. The manufacturing industries of Tur dal generate considerable amount of byproduct/waste in the form of husk. The present investigation explores the possibility of exploiting activated carbon prepared from the Tur dal husk for removing heavy metal. The objective of the work was to enhance the performance of prepared activated carbon by carrying out batch experiments study to optimize the condition of adsorption for complete removal of Cu ions from its 50 ml, 50 ppm solution. The char was produced by carbonizing the washed and dried Tur dal husk in air tight container at 500°C for 1 hr. The obtained char was then activated by soaking in concentrated sulfuric acid (1:1 ratio) for 24 hr. at room temperature to get activated carbon. The physicochemical characterization of achieved activated carbon was done for various parameters along with analysis of trace elements (ICP), crystal nature (XRD) and structural morphology (SEM). The optimum condition for adsorption was studied by altering pH (2-10), agitation speed (50-250 rpm), temperature (10-60°C), adsorbent dose (0.1- 2.25 g) and contact time (0.5-4 hr.). The work concludes activated carbon prepared from Tur dal husk possess considerable metal adsorption property and showing maximum activity in an optimum condition of 6 pH, 200 rpm agitation speed, 10°C temperature, 2.25 g adsorbent dose and 3 hr. contact time. The examination of thermodynamic data confirmed the adsorption by the developed activated carbon was exothermic (positive H0), changing from spontaneous to non-spontaneous with increase temperature (both negative and positive G0), making system ordered and feasible (positive ) through adsorption. The work suggests way of giving value addition to pulse processing industry waste for their better utilization in eco-friendly and economical way.