In 1-chloro-2,4-dinitrobenzene (CDNB) manufacture, the washing process discharges a large amount of CDNB-rich acidic effluent: a very aggressive and toxic wastewater. The concentration of CDNB reaches up to 332.2mg/L. CDNB has been known as an intracellular glutathione-depleting agent and shown to have an adverse effect on erythrocyte membrane integrity and caused aemolysis of human red blood cell. 1 Its removal from wastewater is necessary for health and environmental reason.Two main techniques have been used for the decontamination of CDNB-containing wastewater:activate-carbon adsorption and biodegradation. Biodegradation method works well in summer.However in winter, the activity of animalcules decreases dramatically with the dropping of temperature. Adsorption of CDNB on fresh active-carbon is quick and efficient. However once saturated, active-carbon loses adsorption capacity sharply. The revival of active-carbon by flash steam blowing or sweeping proves to be sluggish and inefficient. Therefore frequent change and replenish of active-carbon is necessary which results in significant operating cost.In this study, we disclose an easy-operating and sustainable method for the treatment of CDNB-contaminated wastewater, which not only removes the toxic CDNB from wastewater and readily revives the active-carbon, but also produces another useful chemical 2,4-dinitrophenol(DNP). Our method is based upon the physical adsorption of CDNB on active-carbon and the chemical conversion of CDNB to SDNP and then to DNP. As a well known nucleophilic substitution example, chlorobenzene with one/two/three NO2, a very strong electron-withdrawing group, at its ortho- and/or para- positions can be readily hydrolysed to give the corresponding phenols under basic condition (Scheme 1).First, the CDNB-contaminated wastewater was treated with active-carbon at room temperature.CDNB was thus adsorbed on to active-carbon physically. The CDNB-loaded active-carbon was filtered off. The acidic filtrate was neutralised by aqueous Ca(OH)2 to give recyclable water or environmental friendly wastewater.Second, the loaded active-carbon was refluxed with aqueous alkaline which converts CDNB into water-soluble sodium 2,4-dinitrophenolate (SDNP). CDNB was therefore desorbed from active-carbon. Filtration of the suspension while hot followed by washing with hot water led to the revival of active-carbon. The revived active-carbon showed similar adsorption capacity to the fresh counterpart and can be recycled to treat the wastewater again and again. Third, acidification of the filtrate containing SDNP to pH = 4 led to nearly quantitative precipitation of DNP as crystals, which can be collected by filtration as another useful dye intermediate.