This graphical abstract describes in general the treatment processes of dye-polluted water using the prepared samples. Activated carbon undergoes both adsorption and catalytic oxidation processes, further the photocatalytic efficiency of each catalyst supported by activated carbon enhanced the removal of dye completely in a short time in addition to adsorption process in the early irradiation time.

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In this work, a low cost preparation scheme of Na-A zeolite from low cost materials was described. Aluminum scrubs were used to prepare sodium aluminate. Commercial sodium silicate and sodium aluminate were then used in the synthesis of zeolite through hydrothermal method under mild conditions. X-ray fluorescence (XRF), X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were employed to confirm the synthesis of pure Na-A zeolite phase. The specific surface area (BET) of the prepared zeolite has also been measured. Results indicated that zeolite has relatively high surface area (=374 m 2 /g). The performance of the prepared zeolite in the removal of Cd 2+ , a highly toxic heavy metal, from water was investigated. The removal of Cd 2+ from water which occurred through precipitation and ion exchange mechanisms was seen to be more efficient comparing to the previous studies. The maximum sorption capacity of Cd 2+ was found to be 54.05 meq/100 g according to the Langmuir isotherm model. However, the sorption capacity was found to be 84.09 meq/100 g after 4 repetitions which is attributed to the ease of reaching the Cd 2+ ions to the inner pores of zeolite upon using slightly dilute Cd 2+ solutions in each repetition.

I N THIS paper, carbonaceous hydrochar adsorbents with highly functionalized surface active sites were prepared from cellulose and lignin constitutes of rice straw via hydrothermal treatment at 180 o C for 20hr followed by carbonization process at 500 o C for 2hr without external gas flow. Two carbonaceous samples were obtained from cellulose and lignin and denoted as RC-C and RL-C, respectively. The resulting hydrochar adsorbents were characterized using means of SEM, TEM, FTIR, Boehm's titration and adsorption of N 2 gas at -196 o C. Kinetic and equilibrium adsorption studies using methylene blue (MB) dye as model pollutant compound in industrial wastewaters were determined. The calculated adsorption efficiencies of the adsorbents were considerably depended on the initial dye concentration, contact time and temperature. The obtained adsorption results were found to describe well using the pseudosecond order kinetic and Langmuir isotherm models. Monolayer adsorption capacity of RC-C and RL-C reached to 100 and 40 mg/g towards MB dye, respectively. Based on these findings, the produced hydrochars from cellulose and lignin of rice straw can be emerged as low-cost and valuable adsorbents for removing dye contaminants from wastewater.

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