Aims Heavy metals are one of the most important pollutants in earth and water environments due to long-term durability. The aim of this study was to isolate phosphate solubilizing bacteria from metal waste, investigate the amount of resistance, remove the metal by it and the effect of phosphatase on removal of metals. Materials & Methods In this experimental study, the isolation of phosphate solubilizing bacteria and detection of isolates were carried out, using biochemical and molecular tests. The phosphatase was measured by colorimetric method, the resistance of the separated to the metals with the minimum inhibitory concentration (MIC50), minimum bactericidal concentration (MBC) and the rate of removal of metals by atomic absorption was measured. The surface changes of the exposed metal cells were investigated by Fourier Transform Infrared Spectroscopy (FTIR) and the effect of phosphatase on metal removal. Data analysis was done with Duncan’ s test, using Excel 2013 and SPSS 20 software. Findings Serratia proteamaculans was identified as producer of the acid phosphatase. The highest MIC and MBC were obtained for Nickel (Ni) and Lead (Pb), respectively. The most metal removal was for Pb. MIC50 of Chrome and Cadmium were obtained less than 0. 1mM and 1mM, and their removal percentage by the isolate were 18% and 48%, respectively. According to the FTIR, 988. 339cm-1 wavelength was observed in the cells treated by 5mM Pb that is related to the Pb3(PO4)2. The isolate showed the highest resistance and removal of Pb. The mechanism of Ni removal was associated to the cell surface, while Pb was removed by both of the cells and supernatant containing phosphatase. Conclusion Serratia proteamaculans is the phosphate solubilizing bacterium in metal waste. This bacterium produces an enzyme called phosphatase, which is a cause of lead removal.

In this study metal oxide nano powder namely NiO nanopowder was prepared .The produced metal oxide was characterized and used as potential adsorbent for the removal of Pb and Zn from aqueous solution. The rate of uptake of the Pb and Zn are rapid in the beginning and the time required for equilibrium adsorption is 120 min .The time of equilibrium as well as time required to achieve a definite fraction of equilibrium adsorption is independent of initial concentration. The results showed that the removal of Pb increased significantly as the pH increased from 2.0 to 6.0 and approach a plateau at pH range of 6.0-9.0., while the removal of Zn increased significantly as the pH increased from 2.0 to 9.0. The adsorption of pb onto NiO follows the Langmiur isotherm, while the adsorption of Zn onto NiO follows the Freundlish isotherm. The pseudo second order kinetic model provided good correlation for the adsorption of Pb onto NiO nanopowder while the pseudo first order kinetic model provided good correlation for the adsorption of Zn onto NiO nanopowder.

Batch adsorption process was employed to remove copper(II) and cadmium(II) ions from contaminated water using dried orange peel powder as a cellulosic adsorbent, which supports circular economy and sustainability. Metal ion concentrations were determined using a flame atomic absorption spectroscopy (FAAS). Effects of pH, sorbate-sorbent contact time, metal ion concentration and adsorbent dose on the removal efficiency of the metal ions was investigated. The adsorption equilibrium was reached at 120 and 150 minutes for Cu(II) ions and Cd(II) ions, respectively. At optimized pH and biosorbent load, 10 mg L-1 of Cu(II) and Cd(II)  ions could be removed to the extent 96.9% and 98.1%, respectively, within 2 hrs. However, the percentage removal of metal ions decreased with increasing their initial concentrations. The observed adsorption data was also interpreted in terms of Langmuir and Freundlich adsorption isotherm models. The calculated equilibrium data fitted more adequately with Freundlich model (higher correlation coefficient, R2) than Langmuir model, indicating heterogeneity of adsorption sites due to different functional groups in cellulose. Cd(II) ions showed less binding affinity and less desorption than Cu(II) ions. The maximum adsorption capacity (qmax) of dried orange peel were 2.78 mg/g and 2.57 mg/g for copper(II) and cadmium(II) ions, respectively.