Competitive effects on mercury removal by an agricultural waste: application to synthetic and natural spiked waters

Abstract

In this work, the efficiency of a local and highly, available agricultural waste, the raw rice husk, was used to remove mercury (Hg) from synthetic and natural waters, spiked with concentrations that reflect the contamination problems found in the environment. Different operating conditions were tested, including initial pH, ionic strength, the presence of co-ions (cadmium) and organic matter. The sorption efficiency of rice husk was slightly affected by the presence H+ ions (pH range between 3 and 9), but in the presence of NaNO3 and NaCl electrolytes and in binary solutions containing Cd2+ and H2+, the sorption efficiency was dependent on the nature and levels of the interfering ion and on the initial concentration of Hg+ used. Nevertheless, in a situation of equilibrium the effect of those ions was negligible and the removal efficiency ranged between 82% and 94% and between 90% and 96% for an initial Hg2+ concentration of 0.05 mg L(-1) and 0.50 mg L(-1), respectively. In more complex matrices, i.e. in the presence ofhumic substances and in natural river waters, the speciation and dynamics of Hg was changed and a fraction of the metal becomes unavailable in solution. Even then, the values obtained for Hg removal were satisfactory, i.e. between 59% and 76% and 81% and 85% for an initial concentration of Hg2+ of 0.05 and 0.50 mg L(-1), respectively.

Multifunctional Binding Chemistry on Modified Graphene Composite for Selective and Highly Efficient Adsorption of Mercury

“…River water is a complex matrix comprising of various ions which can compete for available binding sites on the sorbent. Moreover, the presence of organic matters in this natural system restricts the mobility of mercuric ions and complicates the adsorption of Hg­(II) onto the sorbent. , Nevertheless, the experimental results revealed that the adsorption efficiency of Cyst-prGO was only slightly affected under this complex natural aquatic system. In spite of the lower specific surface area of Cyst-prGO (672 ± 1.0 m 2 g –1 ) compared to GO­(900 ± 1.0 m 2 g –1 ), a great removal efficiency of 91% was achieved in relation to GO (18%) in this real application study.…”

Photocatalytic decomposition of humic acids in anoxic aqueous solutions producing hydrogen, oxygen and light hydrocarbons

“…pesticides. [40] Bonding makes the toxics soluble in complex form and thus difficult to remove by conventional water treatment methods. [41] Waste streams, such as landfill leachates, or natural surface waters containing sufficient quantities of HS, may be of great interest for the production of clean non-fossil fuel, hydrogen, with HS serving as a sacrificial electron donor in photocatalytic water splitting: non-biodegradable waste decomposition and fuel production by a cost-efficient method are achieved simultaneously.…”

Use of red mud (bauxite residue) for the retention of aqueous inorganic mercury(II)

“…At low pH, the competition between increasing Na + concentrations and the fraction of Hg 2+ / HgOH + species that interacts through outer-sphere complexes for the sites of the RM surface and the enhanced electrical double layer surrounding the adsorbent particles acting as a shield that hinders the access of Hg 2+ to the surfaces could be responsible of this behaviour (Ghodbane and Hamdaoui 2006;Rocha et al 2014). Also, the observed sorption behaviour points to an increase of the net surface positive charge of RM at higher ionic strengths of NaNO 3 electrolyte at pH< pH pzc , as in the case of simple Fe oxides (Dzombak and Morel 1990;Stumm and Morgan 1996) or as also described for RM titrated in CsCl solutions (Atun and Hisarli 2000).…”