The present study evaluates the capacity of shrimp (Farfantepenaeus aztecus) head to remove toxic Ni(II) ions from aqueous solutions. Relevant parameters that could affect the biosorption process, such as shrimp head pretreatment, solution pH level, contact time and initial Ni(II) concentration, were studied in batch systems. An increase in Ni(II) biosorption capacity and a reduction in the time required to reach Ni(II) biosorption equilibrium was manifested by shrimp head biomass pretreated by boiling in 0.5 N NaOH for 15 min; this biomass was thereafter denominated APSH. The optimum biosorption level of Ni(II) ions onto APSH was observed at pH 7.0. Biosorption increased significantly with rising initial Ni(II) concentration. In terms of biosorption dynamics, the pseudo-second-order kinetic model described Ni(II) biosorption onto APSH best. The equilibrium data adequately fitted the Langmuir isotherm model within the studied Ni(II) ion concentration range. According to this isotherm model, the maximum Ni(II) biosorption capacity of APSH was 104.22 mg/g. Results indicate that APSH could be used as a low-cost, environmentally friendly, and promising biosorbent with high biosorption capacity to remove Ni(II) from aqueous solutions.

Divalent nickel [Ni(II)] is a heavy metal widely used in several industrial processes. This metal causes serious environmental and public health problems; for this reason it is convenient to treat the industrial wastewaters polluted with nickel before discharging them to water bodies and/or soil. Biosorption is a potential alternative for the treatment of industrial effluents and aquatic ecosystems polluted with heavy metals. In this work, a low-cost, inactive biological material capable of removing divalent nickel from aqueous solutions was selected. Furthermore, the biosorption process catalyzed by the selected biomaterial was kinetically characterized and mathematically modeled.Of the 36 inactive biological materials tested in this work, shrimp head was the one that exhibited the best divalent nickel biosorption characteristics, so this material was selected to carry out further studies.The shrimp head was subjected to different chemical pretreatments with the purpose of increasing its metal biosorption capacity. Most of the tested pretreatments had a negative effect on nickel biosorption; nevertheless, the pretreatment of shrimp head with NaOH 0.5N at boiling temperature for 15 min significantly increased its capacity, which was 134% higher than that of the untreated-biological material.The highest divalent nickel biosorption capacity by 0.5N NaOH-pretreated shrimp head was obtained at an initial pH of 7.0.The divalent nickel removal kinetic profiles exhibited by the shrimp head were satisfactorily described by a pseudosecond-order model, which suggests that the metal is chemically retained by the biological material. Langmuir model adequately represented the nickel biosorption isotherm and the maximum divalent nickel removal capacity predicted by this model [104.22 mg Ni(II) g −1 biosorbent] was closer to the obtained experimentally [96.77 mg Ni(II) −1 biosorbent].The results suggest that the 0.5N NaOH-pretreated shrimp head could be potentially useful for the removal of divalent nickel ions from aqueous solutions.Chromium is released into the environment by a large number of industrial effluents. This heavy metal is of major concern because of its large usage in developing countries and its nondegradability nature. Biosorption of heavy metals by biomaterials has been suggested as a promising technology for effective removal and recovery of heavy metals from aqueous solutions. The present work aims to investigate the hexavalent chromium [Cr(VI)] and total chromium removal by Prunus domestica bark.The Cr(VI) and total chromium removal capacity and volumetric rate of P. domestica bark decreased as the size of the particles increased from 0.15-0.18 mm to 1.41-1.7 mm. It was observed that the residual total chromium concentration was higher than the residual Cr(VI) concentration at all particle sizes and contact times tested, which suggests that the P. domestica bark was capable of reducing the highly toxic Cr(VI) to the less toxic trivalent chromium [Cr(III)].Pretreatment of P. domestica bark with hydrochloric ...