A new adsorbent modified from orange peel (OP) was successfully synthesized by ethylenediamine crosslinking method to remove Cr(VI) from wastewater. The modified orange peel powder (MOPP) was investigated in a batch adsorption system, including both equilibrium adsorption isotherms and kinetics. Effects of several factors, including adsorbent dose, initial pH and Cr(VI) concentration were studied. The data indicated that the pH was not an essential factor that affected the adsorption process, it has a wide pH range from 4 to 10, and high adsorbent dose and lower Cr(VI) concentration could increase the Cr(VI) removal efficiency. Equilibrium data were analysed using the Langmuir, Freundlich and Temkin isotherm models and found to be well represented by the Langmuir isotherm model. The maximum capacity (qmax) obtained from Langmuir model was 52.08 mg/g at pH 6.0. The kinetics of adsorption followed the pseudo-second-order kinetic equation. The results suggest that MOPP is an inexpensive and efficient adsorbent for removing Cr(VI) from aqueous solution.

In this study, the applicability of electrocoagulation using iron electrodes in real dyeing wastewater treatment was assessed based on pollutants removal efficiency, sludge generation, energy consumption and operation cost in practice. The effects of current density, pH, conductivity, and reaction time on treatment performance were evaluated. The operation cost of electrocoagulation was calculated including the energy cost, the iron plate cost, generated sludge treatment cost, and added substances cost. The results indicated that the colour, CODcr and TSS removal efficiencies were high and quite stable with short reaction time (reached 92.07 ± 1.21%, 65.7 ± 1.47%, and 89.8 ± 1.2%, respectively, with only 15 min). Average sludge generation, specific energy consumption, and operation cost were determined respectively as 0.645±0.0543 kg/m3, 1.182 kWh/m3 and 0.517 USD/m3. Coagulation-flocculation using FeSO4 was performed as a control experiment as well. Compared to coagulation-flocculation, electrocoagulation has the same removal efficiency but has less generated sludge (only 50%) and little to no added chemicals. Therefore, the operating cost was quite less than the others, with only 0.517 USD/m3 instead of 1.99 USD/m3 (equal to 1/3.5).

Unavoidably, the expansion of industry causes the release of numerous heavy metals, radionuclides, and organic pollutants into the environment. Due to these pollutants, the extremely toxic, highly carcinogenic chemicals provide a serious risk to people and aquatic life. Wastewater pollutants must be removed to safeguard the ecology. A huge specific surface area, multiple binding sites, a plethora of functional groups, variable pore size, and simplicity of surface modification are just a few advantages of porous materials. They are considered viable candidate materials for the efficient and selective removal of contaminants from aqueous solutions in a range of difficult circumstances due to their benefits. This work reviews the characteristics, methods of functionalization, and ways of modification of many novel porous materials in recent years. The use of these porous materials in the treatment of wastewater was examined. The development potential of porous materials is finally summed up.