Biological removal of Cr(VI) using Fusarium solani in batch and continuous modes of operation

A Comprehensive Review of the Current Progress of Chromium Removal Methods from Aqueous Solution

Chromium (Cr) exists in aqueous solution as trivalent (Cr³⁺) and hexavalent (Cr⁶⁺) forms. Cr³⁺ is an essential trace element while Cr⁶⁺ is a dangerous and carcinogenic element, which is of great concern globally due to its extensive applications in various industrial processes such as textiles, manufacturing of inks, dyes, paints, and pigments, electroplating, stainless steel, leather, tanning, and wood preservation, among others. Cr³⁺ in wastewater can be transformed into Cr⁶⁺ when it enters the environment. Therefore, research on Cr remediation from water has attracted much attention recently. A number of methods such as adsorption, electrochemical treatment, physico-chemical methods, biological removal, and membrane filtration have been devised for efficient Cr removal from water. This review comprehensively demonstrated the Cr removal technologies in the literature to date. The advantages and disadvantages of Cr removal methods were also described. Future research directions are suggested and provide the application of adsorbents for Cr removal from waters.

Wheat Straws and Corn Straws as Adsorbents for the Removal of Cr(VI) and Cr(III) from Aqueous Solution: Kinetics, Isotherm, and Mechanism

In this paper, the adsorption properties of wheat straw (WS) and corn straw (CS) for Cr(VI) and Cr(III) in solution were studied. The effects of adsorption time, pH of the solution, temperature, and initial concentration of metal ions on adsorption capacity were investigated. The adsorption mechanism was discussed. The results showed that the adsorption isotherms of WS and CS for Cr(VI) and Cr(III) satisfied the Langmuir equation. By fitting the Langmuir equation, the saturated adsorption capacity of WS for Cr(VI) and Cr(III) can reach 125.6 and 68.9 mg g^-1, and that of CS for Cr(VI) and Cr(III) can reach 87.4 and 62.3 mg g^-1 , respectively. The adsorption kinetics conformed to the pseudo-second-order kinetic equation. The effect of temperature on the adsorption capacity was not significant. Physical diffusion and chemical adsorption coexist in the process of adsorption of metal ions by straws, and chemical adsorption is dominant, and the effect of physical diffusion on the chemical adsorption rate can be neglected. It can be seen from the experimental results that the treatment of chromium-containing wastewater by using cheap and easily available wheat straw and corn straw had a remarkable effect. The adsorbed straw could be completely desorbed and had excellent recyclability, indicating that the straws are ideal adsorbents.

Preparation and characterization of functionalized silica spheres for removal of Cu(ii), Pb(ii), Cr(vi) and Cd(ii) from aqueous solutions

Functionalized silica spheres (SMS) with mesoporous structure were fabricated through a facile and environmentally benign route, and exhibited remarkable removal efficiency for metal ions from aqueous solutions.

Compost as a source of microbial isolates for the bioremediation of heavy metals: in vitro selection

Heavy metal pollution has become a major environmental concern nowadays and the bioremediation of polluted habitats is an increasingly popular strategy due to both its efficiency and safety. A screening and selection protocol based on different composting processes was designed in order to isolate heavy metal-resistant microorganisms. A collection of 51 microorganisms was obtained and most of them showed the capability to tolerate heavy metals in multi-polluted aqueous systems (Cd(II), Cr(VI), Ni, Pb, Zn(II)), as well as to remove them. The highest detoxification ratios were observed for Pb. Some of the isolates detoxifying more than a 90% of this metal, while the other metals were removed in a range between 20% and 60%. The best isolates (Graphium putredinis, Fusarium solani, Fusarium sp. and Penicillium chrysogenum) were further assayed in order to determine the predominant removal mechanism and the potential use of their dead biomass as a biosorbent. Intracellular accumulation was the prevalent mechanism for most isolates and metals, with the exception of Ni. In this case, the proportion removed by extracellular adsorption was similar or even higher than that removed by intracellular accumulation. Thus, the efficiency of living cells was higher than that of dead biomass except in the case of Ni.

Use of response surface methodology (RSM) in the evaluation of growth and copper(II) bioaccumulation properties of Candida utilis in molasses medium

The influential factors on simultaneous growth and copper(II) bioaccumulation by growing cells of Candida utilis yeast under various ambient conditions, such as changing concentrations of molasses sucrose and copper(II) were tested. The highest growth rate of 0.133 h(-1) was obtained at an initial sucrose concentration of 15 g l(-1) in absence of copper(II). For each constant sucrose concentration chosen between 5 and 15 g l(-1), the increase in initial copper(II) concentration up to 500 mg l(-1) resulted in a decrease in the percentage uptake of copper(II) and moreover all copper(II) concentrations tested inhibited the yeast growth. On the other hand, at each constant copper(II) concentration studied, both the growth and copper(II) uptake yield enhanced with raising sucrose concentration up to 15 g l(-1). Maximum uptake yield of 34.2% was observed in 15 g l(-1) sucrose and 50 mg l(-1) copper(II) containing growth medium. The binary effects of initial sucrose and copper(II) concentrations on the specific growth rate and copper(II) uptake yield of yeast were analyzed by experimental design method and two model equations for predicting the growth rate and copper(II) uptake yield of yeast due to arbitrarily chosen sucrose and copper(II) concentrations were developed by using response surface methodology (RSM).