Environmentally Friendly Adsorbents

Abstract

Contamination of organic and inorganic substances in water, such as heavy metal ions and dyes, is found in almost every country, including developed and developing countries. The presence of these pollutants in the environment frequently resulted in negative effects on the human body and also ecosystem. So far, many technologies to remove pollutants, filtration, precipitation, ion exchange, phytoremediation, adsorption, and so on have been developed. Among these, adsorption is regarded as one of the most promising methods due to its high adsorption capacity and easiness of operation, and then many kinds of adsorbent materials have been researched. The most common adsorbent material used in many places is activated carbon; however, this adsorbent is quite expensive. This chapter introduces some environmentally friendly adsorbents, which are low-cost, safe, and non-harmful adsorbents based on natural products and solid waste materials. Especially, natural materials like plants, solid waste, and agricultural waste investigated in our laboratories are described here. Most of them have the large surface area and some useful functional groups for adsorbing, and then they originally have the high adsorption capacity for pollutants. The treatment of the adsorbents with chemicals like citric acid and phosphoric acid improved their adsorption capacities for metal ions. Some agricultural waste, such as konjac glucomannan, spent coffee grounds, and biochar, have the ability to remove organic compounds and dyes from water. Furthermore, it is introduced that the fermented bark amendment from the thinning of cedar can suppress the uptake of cadmium ion in rice.