Competitive Adsorption of Cu(II) and Zn(II) from Binary Heavy Metal Solutions by Coffee Waste

Abstract

Adsorption process has been proven to be one of the best water treatment technologies globally and activated carbon is undoubtedly considered a universal adsorbent for the removal of a variety of pollutants from water. However, widespread use of commercial activated carbon is often times restricted due to its higher costs. Attempts have been made to develop inexpensive adsorbents utilizing numerous agro-industrial and municipal waste materials. Use of waste materials as low-cost adsorbents is attractive due to their contribution in the reduction of costs or waste disposal, therefore, contributing to environmental protection. In this article was investigated the adsorption behavior of coffee waste when exposed to both single and binary metal component solutions under varying initial concentrations (1000, 500, and 250 ppm) and contact time (3 and 24 hrs.) It is evident from the literature that various low-cost adsorbents have shown good potential for the removal of various pollutants. However, there are few issues and drawbacks on the use of low-cost adsorbents in water treatment that have been discussed in this paper. Additionally, more research is needed to find the practical utility of low-cost adsorbents such as waste coffee on a commercial scale. After the exposure times, the residual concentrations of each heavy metal was determined by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), using EPA Method 6010. Results suggest that the percentage of adsorption of Cu and Zn decreases as the initial metal concentration increases. The coffee waste also has a higher affinity for Cu than Zn ion. The percentages for metal ion removal from the single metal solution are 250 ppm (73.47%), 500 ppm (46.45%), 1000 ppm (27.69%) for copper and 250 ppm (55.08%), 500 ppm (32.78%), and 1000 ppm (21.22%) for zinc. For the competitive metal removal from the binary Cu-Zn solutions, the percentages are 125 ppm (85.67%), 250 ppm (68.93%), and 500 ppm (46.62%) for copper and 125 ppm (49.67%), 250 ppm (7.73%), and 500 ppm (4.59%) for zinc, respectively.