Search

Abstract: In recent years herbicides and heavy metals have surfaced as the most significant environmental pollutants due to rapid industrialization and an increase in population worldwide. While quite effective and efficient, some of the treatment methods, for the removal of these environmental pollutants, involve high operating and maintenance cost along with producing toxic byproducts. Thus, biosorbents have become an attractive alternative to other well established methods. In this study red algae, Gracilaria verrucosa was investigated as a potential biosorbent for the phenoxyalkanoic acid herbicide 2,4-D and the heavy metal Cr(VI). The sorption capacity was found to be 22.3mgg−1 and 113.2mgg−1 respectively. In order to establish the efficiency of G. verrucosa as a biosorbent, sorption tests were conducted with different environmental and process parameters. This study verified that the acid treated biomass, indicates a gradual 47% and 21% increment for 2,4-D and Cr(VI) sorption compared with alkali, formaldehyde, and alcohol treatment. The sorption tests of the red algae G. verrucosa; offer two times more heavy metal removal when compared with low cost biosorbents. Two and three parameter equilibrium models were used to describe the sorption process. Experimental and modeling studies indicate that the sorption process of the investigated sorbents is physisorption with monolayer and endothermic characteristics. Also, surface properties of G. verrucosa were investigated and the effects of the surface active groups were identified. For 2,4 D sorption hydroxyl, carboxyl, and amine and for Cr(VI) sorption hydroxyl, carbonyl, and amino groups were identified as the important surface active groups. [Copyright &y& Elsevier]

Heavy metal adsorption from aqueous solution onto modified biochar derived from date seed biomass was investigated. Modification methods included pre-treatment of the biomass prior to pyrolysis using NaOH and HCl (labelled as DSB-PB and DSB-PA respectively) and post–treatment of the biochar pyrolyzed at 550 °C for 3 h with NaOH and HCl (labelled as DSB-BW and DSB-AW respectively). Modified biochars were compared to unmodified one in terms of their surface chemistry, morphology, metal uptake, and adsorption kinetic behaviour. Scanning electron microscopy images show that acid and base treatment enhanced the biochar porous structure. Fourier-transform infrared spectroscopy revealed that acid treatment had enriched the functional groups such as C C, C O, C O, and phenolic groups on the biochar surface which further facilitated metal ions adsorption. Alkali treatment had less significant impact on the biochar surface functional groups. Modification improved the adsorption capacity for all metals. Most notably, DSB-PA biochar showed the highest adsorption capacities of 0.911, 0.705, and 0.692 mmol g−1 for Pb2+, Cu2+, and Ni2+ respectively. Compared to the unmodified biochar, the adsorption capacities of DSB-PA for Pb2+, Cu2+, and Ni2+ increased by 27%, 66% and 98%, respectively. Sips model adequately described the adsorption isotherms indicating heterogeneous adsorption systems. Adsorption rates of metal ions onto the DSB-PA were fast with almost 94% of the total amount of metals adsorbed within the first hour compared to 3–6 h for unmodified biochar. Pre-treatment of biochar with HCl is an economical method to produce an effective low-cost adsorbent with low environmental impact. [ABSTRACT FROM AUTHOR]