Since the success of the leaching stage depends on the choice of the leach solution and leach conditions, investigations to develop new leach solutions and optimization of leach parameters is being undertaken. Leach solutions employed for Cu recovery include acids, bases, salts, and ionic liquids. Typical acids used for base metal extraction are sulfuric acid , nitric acid , hydrochloric acid , trifluoromethanesulfonic acid , and mixtures of acids . These acids have often been used in combination with oxidants such as oxygen, H2O2, ferric salts, and chlorine gas . Of these leaching agents, sulfuric acid is the favoured solvent predominantly because its market price is lower than the other acids and it has been proven to be an efficient solvent, especially for the recovery of Cu . Ammoniacal mixtures and NaOH are examples of basic leaching agents for Cu recovery. The ammoniacal lixiviant is generally comprised of ammonia in combination with ammonium salts such as carbonates , chlorides , or sulfates . The ammonia leaching process is more suitable for Cu extraction than acidic systems as these lixiviants show higher selectivity for Cu, leaving metals such as iron (Fe) and aluminium (Al) undissolved. However, it has been shown that nickel (Ni) and zinc (Zn) are also dissolved in the ammonia-based lixiviant. Most metals present in PCBs are predominately found in their elemental form or as alloys, therefore requiring oxidative lixiviants such as oxygen or Cu oxide for effective extraction . Salts including chlorides and imidazole-based ionic liquids for Cu recovery have been reported. Despite the attractive features, hydrometallurgy is intrinsically hazardous as the commonly used leaching agents -acids and bases are generally corrosive, difficult to work with, and environmentally unfriendly . To make hydrometallurgy more environmentally friendly, alternatives like organic leaching agents (e.g. citric acid and oxalic acid) have been investigated . Though reported efficiencies of organic leaching agents are worse compared to the inorganic ones, improved leaching efficiencies have been observed in the addition of oxidants like H2O2 to organic acids . Studies reporting on copper recovery from PCBs using a combination of malonic acid and H2O2 as leach solution is rare. In addition, pulverized scrap PCBs are often employed for Cu recovery and studies employing PCB pieces are only emerging. The use of PCB pieces is an attractive option as not only can be Cu leaching process be cheaper and simpler but also the residual PCB piece can be conveniently recycled . Here, we report on the optimization of conditions, specifically malonic acid concentration, H2O2 concentration, and contact time, for Cu leaching from scrap laptop computer-sourced PCB pieces by a mixture of malonic acid and H2O2 (Figure ). First, the average Cu content in each PCB piece was determined by complete digestion in aqua-regia followed by metal content measurement by absorption spectrophotometry. In addition, the optimum Cu leaching parameters were determined from the Box-Behnken design. Finally, theoretical calculations were performed to ascertain the interaction between the leaching agent and Cu.