Pre-treated sawdust charcoal by sulphuric acid had more surface area and porosity than sawdust charcoal. Acid pre-treatment increased the adsorption efficiency because acid could dissolve tars and the components of sawdust charcoal such as K and Ca and resulted in increasing of surface of porous sawdust charcoal. In the adsorption of synthetic reactive dye wastewater containing 400 mg g{sup}(-1) dye solution, 90 g 1{sup}1 of sodium sulphate, 20 g l{sup}(-1) of sodium carbonate, initial pH of 10.5±0.5, H{sub}2SO{sub}4-treated sawdust charcoal could decrease COD from 608 mg l{sup}(-1) to 465 mg l{sup}(-1), whereas sawdust charcoal increased to 626 mg l{sup}(-1). Adjusting the initial pH of dye solution to 2.0 increased dye adsorption in both adsorbents, whereas the adsorption of synthetic reactive dye from wastewater by sawdust charcoal and H{sub}2SO{sub}4-treated sawdust charcoal can adsorb in wide range of initial pH of dye solution (pH 2.0-10.0), In addition, dissolving of K and Ca at the low pH of solution also caused precipitation of potassium hydroxide and calcium hydroxide that enhanced dye adsorption. The maximum adsorption capacity of synthetic reactive dye within wastewater by sawdust charcoal and H{sub}2SO{sub}4-treated sawdust charcoal were 24.28 and 29.92 mg g{sup}(-1), respectively. Pre-treatment of sawdust charcoal by H{sub}2SO{sub}4 could increase the dye adsorption capacity in textile wastewater.
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