In this research removal of chromium from an aqueous solution by multilayer-mixed (reduction/sorption) bed via scrap iron as zero valent iron and charred nutshell (walnut shell) as adsorber were studied. Both batch and continuous system were conducted. The batch system reveals that the adsorption process was of favorable type. Three models were used to describe the adsorption process. Freundlich model is matching well to the data with (R2=0.975). In the continuous system , two  sets of experimental were considered, the first set (multilayer bed) conducted by fixing the characteristics of the scrap iron bed (bed height 0.2 cm, particle size 500 µm) and varying the walnut shell parameters, the optimum value of this set recorded as (bed height 2.5 cm, particle size250µm). While for the second set of experimental after fixing the optimum values of the walnut shell bed and varying the scrap iron bed characteristics, the optimum values were (height 1cm, particle size 500µm as filling). Also, the Mixed bed configuration were studied by conducting the optimum conditions for the previous experiment. it was found that at any certain time the mixed layer offers the maximum efficiency of removal rather than the multi-layer bed.

In this article, the manufacture of low-cost adsorbents from tea and coffee waste for the removal of lead from an aqueous solution was batch experimental of the created adsorbent. After charring tea and coffee waste, there was a considerable improvement in surface area and other physical parameters such as density, bulk density, and porosity.  In the batch studies, different dosages of both adsorbents were utilized, and the equilibrium isotherm was of the very favorable type for adsorbents, and two models (Freundlich and Langmuir) were used, and the data corresponded well with the Freundlich isotherm. a random set of experiments showed a removal degree efficiency of lead reaching (99 percent ).production

In this article, the production of low-cost adsorbents removal of lead from an aqueous solution from tea and coffee waste and a comparison study between them was investigated utilizing a continuous process to explore the kinetic behavior of the created adsorbent. After charring tea and coffee waste, there was a considerable improvement in surface area and other physical properties such as porosity, density, and bulk density. In the continuous system, several parameters such as (bed height, particle size, and flow rate) were tested, and the optimal circumstances (for each experiment) were held constant for the subsequent sets of tests. The optimal circumstances were achieved as follows (bed height=8cm, particle size=250µm, and flow rate 0.5L/hr)and a random set of experiments showed a removal degree efficiency of lead reaching (99 %). As a result, raising bed height and pH will raise the breakpoint value. While reducing the flow rate, initial concentration, and particle size). Increasing the bed height increases the breakpoint value. Particle size will increase the breakpoint as the flow rate decreases. Keywords: Adsorption, Heavy metals , Continuous system, , Lead ions

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