Due to the limitations of traditional adsorbents for dyeing wastewater, this study combined natural adsorbent (CS, chitosan) and hydroxyapatite (HAp) to form a composite for enhancing the adsorption of aqueous Congo red (CR). The chitosan was prepared from crab shells (Somanniathelphusa sinensis) with a deacetylation degree of about 89%. The HAp and HAp-CS composites were prepared by precipitation in high pH (~10) with the help of concentrated ammonia water (25%). The crab shell chitosan and chitin were characterized by the FTIR method, and the HAp and HAp-CS composites were analyzed using the SEM method. The CR adsorption experiments were carried out in batch form and sampled once for each condition. The results showed that the characteristic peaks in the FTIR spectrum confirmed the success of the crab shell chitosan preparation. The HAp and HAp-CS composites possess porous structures and seem to have a high surface area. The CR adsorptions reached optimal after 5-15 min. contacting, the adsorption efficiency tended to decrease with the initial concentration of CR and increase with the adsorbent dosage. The initial pH of the solution affected the adsorption efficiency for the 70%HAp-CS and 30%HAp-CS composites but had almost no effect on the adsorption capacity of 0%HAp-CS and 50%HAp-CS. The 50%HAp-CS composite had the best adsorption capacity among the synthesized composites (qmax = 769.2mg/g). The adsorption isotherm and kinetics best fit the Langmuir isotherm and pseudo-second-order kinetics model.

Heavy metal pollution is a major problems in the environment. The impact of toxic metal ions can be minimized by different technologies, viz., chemical precipitation, membrane filtration, oxidation, reverse osmosis, flotation and adsorption. But among them, adsorption was found to be very efficient and common due to the low concentration of metal uptake and economically feasible properties. In this review paper, Fe–Mn binary oxide incorporated into diatomite (Fe/Mn-diatomite) was prepared by a simple coating method , and removal of Cu(II) from aqueous solutions. The effects of three independent variables including initial ion concentration, removal time, and adsorbent dosage were investigated on the maximum adsorption of Cu (II). The optimum conditions for the adsorption of Cu(II) was obtained: 75 ppm of initial ion concentration, 150 min of removal time and 1.5 g/l of adsorbent. The maximum removal efficiencies of Cu(II) was obtained 86.25%. The results showed that Fe/Mn-diatomite was apable of treating copper metal in wastewater.

Environmental issues such as the wastewater have influenced each aspect of our lives. For human and environmental health protection, it is necessary to remove excess zinc in industrial wastewaters before discharging them to environment. Modified diatomite displayed larger surface area and pore volumes in comparison with untreated natural diatomite, which favored heavy metals sorption behavior. In this study, the removal of Zn(II) ions from aqueous solution was studied using Fe/Mn modified diatomite sample at different adsorption parameters such as contact initial metal ions concentration, dosage of Fe/Mn-Diatomite and ionic strength Na2CO3 on ionic Zn2+ adsorption capacity of diatomite modified. The residual zinc concentration in the solution was determined using flame atomic absorption spectroscopy. The results showed that: the gravitational increase increases with increasing time and then becomes almost stable, with 120 minutes timeliness; absorption increases when Fe/Mn-Ditomite is increased, absorption reaches 89.48% at a dose of 1.5 g/l; additional different concentrations Na2CO3 ranged from 0 ppm to 80 ppm the results showed that performance treatment Zn2+ of correspond 94,85%. This study could lay an essential foundation to develop modified diatomite for heavy metal removal from wastewater.