No abstract

The goal of this study was to investigate the preparation of low-cost activated carbons from bean pods waste and to explore their potential application to the removal of heavy metals from aqueous solutions. Conventional physical (water vapor) activation was used for synthesizing the adsorbent. The obtained carbon was employed for the removal of As (III) and Mn (II) from aqueous solutions at different initial concentrations and pH values. Adsorption for both ions follows Langmuir-type isotherm, the maximum loading capacities for arsenic (III) and Mn (II) ions being 1.01 and 23.4 mg g-1 , respectively. According to the experimental data, it can be inferred that the basic character of the surface, i.e. the high content of basic groups favors adsorption of ions. Arsenic adsorption capacity on the carbon obtained from agricultural waste was found to be similar to more expensive commercial carbons showing high adsorption capability. As regards manganese adsorption, herein obtained carbon presented higher uptake than that of activated carbons reported in the literature.

No abstract

Adsorption of mercury from aqueous solutions using three types of furfural-based carbon adsorbents was studied. After activation with water vapor and air, carbon adsorbents with basic and acidic characters, respectively, were obtained. The results from the study showed that all modifications of the adsorbents (with both basic and acidic characters, as well as an adsorbent from mixture of furfural and apricot stones tar) are efficient sorbent materials for mercury removal from aquatic solutions. Mercury adsorption follows a Langmuir isotherm. Adsorbents with good adsorption capacities (174 mg/g for the basic adsorbent, 154 mg/g for the adsorbent from a mixture of furfural and tar, and 132 mg/g for the adsorbent with acidic character) were obtained. The pH was determined to be the most crucial parameter. The mercury removal increases with an increase in pH from 2 to 5. It was found that the adsorption capacities of the produced carbons are significantly higher than those of commercial activated carbons. A desorption study was performed with hot water. The percentage of the recovery was 6% for the basic furfural adsorbent, 1% for the furfural adsorbent with acidic character, and 4% for the adsorbent from the mixture of furfural and tar.