Wastewater treatment is a global concern nowadays. Although many methods are available for wastewater treatment, the adsorption method has received much more attention from researchers. Significant problems for extending the adsorption method to the industry for wastewater treatment are the high cost of cosmetically available adsorbents, their recovery from the medium, and their regeneration and reuse. Magnetic biosorbents provide easy separation from the treated water at lower prices compared to other commercially available adsorbents. In terms of characteristics and efficiency in the adsorption of organic and inorganic pollutants, magnetic biosorbents have shown growing promise. If biosorbents and the removed contaminants are not handled and disposed properly, they can become causes of environmental pollution. There are numerous review papers on wastewater treatment with magnetic adsorbents. However, this paper provides comprehensive information on the synthesis of magnetic nanoparticles, the magnetization of biosorbents, and the application of magnetic biosorbents for wastewater treatment to pave the avenue for new magnetic biosorbents development that can be scale up from laboratories to the industry.

Pollution of water due to presence of certain heavy metal ions is a severe socio-environmental problem caused by the discharge of industrial wastewater. In view of their toxicity, non-biodegradebility and persistent nature, their removal becomes an absolute necessary. Chromium is one of the major pollutants in the environment and is frequently present in wastewaters from various industrial units. Several conventional physical and chemical treatment techniques may be used for the removal of chromium. However, such processes are not only expensive and highly energy intensive, but also lead to production of harmful by-products and end-products, the ultimate disposal of which again causes secondary pollution. Hence, the potential application of microorganisms as biosorbent for the removal of chromium has been recognized as an alternative to the existing conventional physico-chemical methods. The aim of the present study is to review the removal of chromium from aqueous solution using various materials of agricultural and biological origin , which have been studied as potential chromium biosorbent (plant leaves, saw dust, sugar cane bagassa, sugar beet pulp, maize cob and rice hulls). Also reported cases on chromium removal from aqueous solution by using fungal, algal and bacterial biomass under the growing, resting and dead conditions in batch as well as in continuous bioreactors are reviewed.

This paper reports the potential of chemically treated wood chips to remove copper (II) ions from aqueous solution a function of pH, adsorbent dose, initial copper (II) concentration and contact time by batch technique. The wood chips were treated with (a) boiling, (b) formaldehyde and (c) concentrated sulphuric acid and characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive analysis X-ray. pH 5.0 was optimum with 86.1, 88.5 and 93.9% copper (II) removal by boiled, formaldehyde-treated and concentrated sulphuric acid-treated wood chips, respectively, for dilute solutions at 20 g L-1 adsorbent dose. The experimental data were analysed using Freundlich, Langmuir, Dubinin-Radushkevich and Temkin isotherm models. It was found that Freundlich and Langmuir models fitted better the equilibrium adsorption data and the adsorption process followed pseudo-second-order reaction kinetics. The results showed that the copper (II) is considerably adsorbed on wood chips and it could be an economical option for the removal of copper from aqueous systems.

In this research, the adsorption of phosphoric acid from an aqueous solution was investigated at different temperatures (298, 308, and 318 K) by using different adsorbents such as wheat bran and banana peels, in a batch system. FTIR and SEM analysis were used, in order to determine the functional groups in the structure of adsorbents and the surface characteristics of adsorbents, respectively. In the adsorption experiments, the effect of important parameters such as the effect of contact time, the amount of adsorbent temperature, and initial acid concentration was investigated. Equilibrium time was determined 40 and 50 minutes for wheat barn and banana peels. The highest percentage of adsorption for banana peel and wheat peel was measured at 71% and 59. 8% for 1 g /L phosphoric acid, respectively. The optimum amount of adsorbent was determined 3g. Investigation of the temperature demonstrated that the percentage of removing phosphoric acid decreased by increasing the temperature. Different models of adsorption isotherms such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were applied to analyze the equilibrium data at different temperatures and Langmuir and Temkin isotherm have the most agreement with experimental data for absorbents. Different kinetic models such as pseudo-first order, pseudo-second order, Elovich, and intra-particle diffusion model were chosen to describe the kinetic of adsorption, and the pseudo-second-order model for wheat barn and Elovich for banana peels have the best agreement with experimental data for each adsorbent. Thermodynamic parameters like standard Gibbs free energy changes of adsorption (Δ, G oads), standard enthalpy changes of adsorption (Δ, H oads), and standard entropy changes of adsorption (Δ, S oads) were calculated by using equilibrium constant values at different temperatures. The negative value of (Δ, G oads) demonstrated that adsorption of phosphoric acid by adsorbents is a spontaneity process and negative values of (Δ, H oads) showed that adsorption of phosphoric acid on adsorbents is exothermic. The absorption capacity of banana peel and wheat bran was achieved20 and 11 mg/g, respectively. As a result, banana peel was the appropriate absorbent in this work.