Study On Biological Adsorption Of Heavy Metal Ions In Water

With the deve lopme nt of agric ultura l tech, more and more waste s ofagriculture are discarded in China, a large agricultura l country. For exa mp le,every year500million to ns crop wastes are produced, most of whic h werediscarded or fired d irectly ca us ing green resources waste and environme nta lpollution.With the increasingly serious water po llution, whe n seeking for effic ie nt andenviro nme nt frie nd ly approaches to deal with wastewater, researchers focus oncrop wastes. Crop waster contains ce llulose、he mi-cellulose、 lignin and so on,whic h can provide lots of active functiona l groups, such as hydroxyl、carboxyl、pheno l et al. These active functio na l groups can absorb heavy meta l ions inwastewater.The performa nce of treating wastewater conta ining hea vy meta ls withagricultura l waste used mus hroom substrate was exp lored in this paper. On thebas is of its adsorption, the used mushroo m s ubstrate was che mica lly modified toprepare effic ie nt mod ified mus hroom s ubstrate whic h was used to remo ve copperio ns and nicke l ions fro m wastewater. The influenc ing factors playing the lead ingrole on mod ified effect were stud ied during mod ificatio n, and the optima lmod ified conditio ns were determined. In the static experiments, the adsorptioneffects of mod ified adsorbent on the so lutio ns with copper ions and nickel ions indifferent initia l pH, initia l concentratio n o f copper io ns and nickel io ns, adsorbentamount as well as differe nt absorptio n time co nditions, and the re mo va l effects o funmod ified mushroo m substrate were compared. Fina lly, preliminary stud ied onthe treatment effect o f mod ified adsorbent o n the copper-conta ining wastewaterand its rege neration c haracteristics were carried out in the dyna mic adsorptionexperiment.The results showed that: the adsorptio n abilities of used mus hroom substratemod ified by che mical method in the process of treating the solutio ns with copperio ns and nickel ions were both improved a nd the adsorption speed was faster than before. When the qua lity o f used mus hroom s ubstrate is10g, the optima lconditio ns of the modificatio n process was as follo ws: mod ification te mperature30℃, mod ification time60min,and0.5mo l/L of oxa lic acid solutio n250mL. Inthe static adsorptio n experiment, the adsorption rates of modified adsorbent wereincreased with the increas ing o f initia l pH. The adsorptio n rates were highest(copper ions87.73%and nicke l ions81.59%), when the pH va lues wererespective ly5.0and4.0; and the lower the initia l concentratio n, the better thetreatme nt effect. Whe n the adding a mount of mod ified absorbent was20g/L, thetreatme nt effect was better for50mL10mg/L both ions solutio n and the adsorptionbalance can be achieved after60min. In the best adsorption cond itio ns, thema ximum copper io ns and nicke l ions adsorption rates o f mod ified adsorbent byoxalic ac id were respective ly94.23%and90.42%. When treated by modifiedabsorbent, the wastewater conta ining10mg/L copper ions and10mg/L nicke lio ns can respective ly achieved le ve l2standard of GB8978-1996and the ma ximumpermiss ib le emitting concentratio n of GB8978-1996. In the dyna mic experime nt ofremoving copper ions, the mod ified absorbent by o xa lic acid had better effectwhe n first time us ing tha n rege neration once. This research not only provided ahigh e ffic ient, environme nta l protection and economic processing method forheavy meta l wastewater, but also put forward a new idea o f utilizatio n for the usedmushroom substrates.